To be hesitant is not entirely modest (5)
I believe the answer is:
demur
'to be hesitant is' is the definition.
I can't judge whether this defines the answer.
'not entirely modest' is the wordplay.
'not entirely' means to remove the last letter.
'modest' becomes 'demure' (I've seen this before).
'demure' with its final letter taken away is 'DEMUR'.
Can you help me to learn more?
(Other definitions for demur that I've seen before include "Take exception (to)" , "Hesitation" , "Politely disagree" , "Hesitate from uncertainty or object" , "Dissent, object" .)