Topless females -- a bad sign? (4)
I believe the answer is:
'a bad sign?' is the definition.
(I've seen this before)
'topless females' is the wordplay.
'topless' means to remove the first letter.
'females' becomes 'women' (woman is a kind of female).
'women' with its initial letter taken away is 'OMEN'.
(Other definitions for omen that I've seen before include "premonition" , "Warning token" , "Sign of things to come" , "Forecast" , "Harbinger, prophetic sign" .)