Wings of nylon filled with a strong material (7)
I believe the answer is:
nankeen
'material' is the definition.
(I know that nankeen is a type of material)
'wings of nylon filled with a strong' is the wordplay.
'wings of' suggests removing the centre (letters on the two wings removed).
'filled with' indicates putting letters inside.
'strong' becomes 'keen' (keen can mean strong or intense).
'nylon' with its middle removed is 'nn'.
'nn' going around 'a' is 'nan'.
'nan'+'keen'='NANKEEN'
(Other definitions for nankeen that I've seen before include "hard-wearing stuff" , "Buff colour(ed cloth)" , "Hard-wearing fabric, originally from China" , "Chinese cotton cloth" , "Yellowish stuff" .)