Chemical gear distributed by hospital department (7)
I believe the answer is:
reagent
'chemical' is the definition.
(thesaurus)
'gear distributed by hospital department' is the wordplay.
'distributed' indicates an anagram.
'by' is a charade indicator (letters next to each other).
'hospital department' becomes 'ent'.
'gear' is an anagram of 'reag'.
'reag'+'ent'='REAGENT'
(Other definitions for reagent that I've seen before include "Chemical with known properties" , "What causes change" , "Substance used in chemical analysis" , "Get near (anag) - substance used in chemistry" , "Chemical in reaction" .)