Clement and Origen lived and wrote in Alexandria, which had the distinct reputation for interpreting scripture **with several levels of meaning. **
Scholar Ludwig Ott wrote this: “The Alexandrinians, St. Clement [of Alexandria] and Origen, attest the general belief of the Church that the Lord offers us the partaking of His Body and His Blood. However, due to their penchant for allegory, passages are also found in their writings, in which they use the words body and blood to signify the teaching of Christ, by which our spirits are nourished [Origen is quoted from Contra Celsum VIII,33 cf. In Num hom 7,2; In Exod hom 13,3; In Matt comm ser 85]. As, according to the usage of the Alexandrinians, the same scriptural passage can be variously interpreted, an allegorical interpretation DOES NOT EXCLUDE the possibility of a more fundamental meaning.”
lettersonorthodoxy.wordpress.com/2011/12/03/the-real-presence-of-jesus-in-the-eucharist/: “It is very important to understand what the word ‘symbol’ meant to the Fathers. In the Greek (which is how the majority of the Fathers would be using it), the word does NOT mean substitution or in place of. It is a compound word made up of sym (meaning together) and ballon (meaning to throw). Thus, a symbol is something where two unlike things are thrown together. Thus, the Eucharist is a symbol because the mundane bread and wine are thrown together with the divine presence of Christ. The Eucharist is BOTH bread and wine AND the body and the blood of Christ. This is how it is a symbol"
Therefore, in my opinion, even though Clement and Origen were influenced by the theological allegorizing prevalent in Alexandria, and even though they found several layers of meaning to many, many texts, they both nevertheless believed in a Real Presence of Christ in the Eucharist.
The Eucharist is a symbol, but it is not just a symbol: it also contains—somehow, mysteriously, spiritually but truly—both the Flesh and Spirit of Christ.
Here is a good website for you to look at:
catholicdefense.blogspot.com/2014/02/did-tertullian-deny-real-presence.html