Topless tart showing some brass (7)
I believe the answer is:
trumpet
'brass' is the definition.
(I've seen this before)
'topless tart' is the wordplay.
'topless' means to remove the first letter.
'tart' becomes 'strumpet' (I've seen this before).
'strumpet' with its first letter taken away is 'TRUMPET'.
'showing some' acts as a link.
(Other definitions for trumpet that I've seen before include "Daffodil corona" , "Shout!" , "Proclaim loudly" , "Loud cry" , "Centre of daffodil flower" .)