Crowd with redhead in skimpy garment (6)
I believe the answer is:
throng
'crowd' is the definition.
(I know that throng is a more specific form of crowd)
'redhead in skimpy garment' is the wordplay.
'redhead' becomes 'r' (head letter of 'red').
'in' means one lot of letters goes inside another.
'skimpy garment' becomes 'thong' (type of undergarment).
'r' inserted into 'thong' is 'THRONG'.
'with' acts as a link.
(Other definitions for throng that I've seen before include "Mob" , "Large gathering of people" , "A great crowd of people" , "Large crowd or host" , "Densely packed crowd" .)