In these skimpy knickers host shows no resistance (5)
I believe the answer is:
thong
'in these skimpy knickers' is the definition.
The definition suggests an adverb but the answer is not.
'host shows no resistance' is the wordplay.
'host' becomes 'throng' (both can mean a large group of people).
'shows no' is a deletion indicator.
'resistance' becomes 'r' (electronics abbreviation).
'throng' with 'r' taken out is 'THONG'.
(Other definitions for thong that I've seen before include "Lash of whip" , "Frequently (archaic)" , "Leather strip fastener" , "Beachwear item" , "What offers little coverage" .)