Search for a company doctor (4)
I believe the answer is:
comb
'search' is the definition.
(I know that comb is a more specific form of the action search)
'company doctor' is the wordplay.
'company' becomes 'co' (abbreviation).
'doctor' becomes 'mb' (Bachelor of Medicine, Medicinae Baccalaureus).
'co'+'mb'='COMB'
'for a' acts as a link.
(Other definitions for comb that I've seen before include "Systematically search" , "Common hair tidier" , "Toothed device - crest" , "Crest on the head of some birds" , "Ransack, scour" .)