One of Grumpy's cohorts (3)
I believe the answer is:
doc
'one of grumpy's cohorts' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for doc that I've seen before include "Medic (colloq.)" , "Medical practitioner (abbr)" , "Quack" , "Medic (familiar)" , "GP (informal)" .)