Clamp down on work force (7)
I believe the answer is:
oppress
'clamp down on' is the definition.
(thesaurus)
'work force' is the wordplay.
'work' becomes 'op' (abbreviation for opus).
'force' becomes 'press' (I've seen this in other clues).
'op'+'press'='OPPRESS'
(Other definitions for oppress that I've seen before include "Vitality" , "Afflict" , "Treat harshly" , "Lie heavy upon" , "Bear down hard on" .)