Branch of pharmacy (3)
I believe the answer is:
arm
'branch' is the definition.
(thesaurus)
'of pharmacy' is the wordplay.
'of' says the answer is hidden in the clue.
'ARM' is hidden in the letters of 'pharmacy'.
(Other definitions for arm that I've seen before include "Ram into limb" , "Division of company" , "Sleeve" , "Human limb" , "Activate warhead" .)