Wonga initially in till for material (5)
I believe the answer is:
twill
'for material' is the definition.
(twill is a kind of material)
'wonga initially in till' is the wordplay.
'initially' says to take the initial letters.
'in' means one lot of letters goes inside another.
The first letter of 'wonga' is 'w'.
'w' placed inside 'till' is 'TWILL'.
(Other definitions for twill that I've seen before include "Ribbed cloth" , "Strong woven fabric" , "Strong ridged fabric" , "Fabric woven to have diagonal ribs" , "Fabric with distinctive weave" .)