Section of prenup re-energised groom (5)
I believe the answer is:
preen
'groom' is the definition.
(a bird grooms itself by preening feathers)
'section of prenup re-energised' is the wordplay.
'section of' indicates the answer is hidden within the clue.
'PREEN' is hidden in the letters of 'prenup re energised'.
(Other definitions for preen that I've seen before include "Arrange feathers" , "Vainly groom oneself" , "Tidy/clean (feathers)" , "Perfect one's appearance" , "Clean with the beak" .)