Set of clothing (4)
(Other definitions for suit that I've seen before include "Do as you please!" , "Formal wear for men" , "diamonds possibly" , "Formal clothing" , "See 7" .)
'set of clothing' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for outfit that I've seen before include "Costume" , "complete set of equipment" , "Cohesive unit, eg a military company" , "Ensemble of clothes" , "Complete set of clothes" .)