Topless bather's new suit (6)
I believe the answer is:
hearts
'suit' is the definition.
(hearts is a playing card suit)
'topless bather's new' is the wordplay.
'topless' means to remove the first letter.
'new' indicates an anagram.
'bathers' with its first letter taken off is 'athers'.
'athers' is an anagram of 'HEARTS'.
(Other definitions for hearts that I've seen before include "Playing-card suit" , "Vital organs in the pack" , "Body pumps" , "Soccer club" , "Central parts" .)