A sometimes prominent feature too big for trousers (6)
I believe the answer is:
chinos
'for trousers' is the definition.
(chinos are a type of trousers)
'a sometimes prominent feature too big' is the wordplay.
I cannot really see how this works, but
'feature' could be 'chin' (facial feature) and 'chin' is present in the answer.
'big' could be 'os' (abbreviation for oversize) and 'os' is located in the answer.
No letters remain.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for chinos that I've seen before include "Trousers made from a twilled cotton" , "Casual cotton trousers" .)