Many Londoners wearing this material (5)
I believe the answer is:
nylon
'this material' is the definition.
(nylon is a kind of material)
'many londoners wearing' is the wordplay.
'wearing' indicates a hidden word (the answer is covered by or 'wearing' the clue).
'NYLON' is hidden in the letters of 'many londoners'.
(Other definitions for nylon that I've seen before include "Synthetic polymer" , "Synthetic cloth" , "Type of material" , "Artificial material" , "Man-made fibre" .)