Caper left one in short dress (6)
I believe the answer is:
frolic
'caper' is the definition.
('frolic' can be a synonym of 'caper')
'left one in short dress' is the wordplay.
'left one' becomes 'li' (left abbreviation plus 1).
'in' indicates putting letters inside.
'short' means to remove the last letter.
'dress' becomes 'frock' (frocking is a kind of dressing).
'frock' with its final letter removed is 'froc'.
'li' going into 'froc' is 'FROLIC'.
(Other definitions for frolic that I've seen before include "Play about in lively cheerful way" , "Caper, gambol" , "Move in a cheerful and lively way" , "fun" , "High jinks" .)