Search thoroughly for groom (4)
I believe the answer is:
comb
I believe this clue is a double definition.
'search thoroughly' is the first definition.
(synonyms)
'for groom' is the second definition.
(combing is a way of grooming oneself)
(Other definitions for comb that I've seen before include "Implement with teeth" , "Tidy (hair); some honey" , "Ransack, scour" , "Toothed device - crest" , "Something with teeth (for the hair!)" .)