Hesitation takes time to be keen (5)
I believe the answer is:
eager
'keen' is the definition.
(thesaurus)
'hesitation takes time' is the wordplay.
'hesitation' becomes 'er'.
'takes' indicates putting letters inside.
'time' becomes 'age' (age is a kind of time).
'er' going around 'age' is 'EAGER'.
'to be' acts as a link.
(Other definitions for eager that I've seen before include "Anxious" , "Sharp" , "Keen, avid" , "Keenly interested" , "Longing to see" .)