Beast seeming to claim to be ten (4)
I believe the answer is:
ibex
'beast seeming' is the definition.
Although both the answer and definition are singular nouns, I don't understand how they can define each other.
'claim to be ten' is the wordplay.
'claim' becomes 'i' (I can't explain this - if you can you should believe this answer much more).
'ten' becomes 'X' (Roman numeral).
'i'+'be'+'x'='IBEX'
'to' acts as a link.
Can you help me to learn more?
(Other definitions for ibex that I've seen before include "being nimble-footed" , "Wild goat of North Africa" , "Mountain-goat" , "one seldom puts a foot wrong" , "Large-horned wild goat" .)