Could possibly be or sound like a very small creature (5)
I believe the answer is:
might
'could possibly' is the definition.
('could' can mean 'might')
'sound like a very small creature' is the wordplay.
'sound like' shows a homophone (sound like).
'a very small creature' becomes 'mite' (I've seen this before).
'mite' sounds like 'MIGHT'.
'be or' acts as a link.
I am not very happy about this link. Some or all of it may be part of another bit of the clue.
Can you help me to learn more?
(Other definitions for might that I've seen before include "Clout" , "It expresses possibility" , "Great power/strength" , "word expressing possibility" , "Powerfulness" .)