Seductress about to be caught in sin (5)
I believe the answer is:
siren
'seductress' is the definition.
(I've seen this before)
'about to be caught in sin' is the wordplay.
'about' becomes 're' ('re' means regarding or about).
'to be caught in' is an insertion indicator.
're' inserted inside 'sin' is 'SIREN'.
(Other definitions for siren that I've seen before include "Bewitching singer" , "Seductive woman" , "Alarm - charming female" , "'Delilah!'" , "Temptress; warning signal" .)