As many as there can be (5)
I believe the answer is:
three
'as many' is the definition.
Both the answer and definition are adjectives. Perhaps there's an association between them I don't understand?
'there can be' is the wordplay.
'can be' is an anagram indicator.
'there' is an anagram of 'THREE'.
'as' is the link.
Can you help me to learn more?
(Other definitions for three that I've seen before include "Trinity, triad" , "There (anag.)" , "trilogy" , "III" , "Prime number" .)