Having been given material backing? (5)
I believe the answer is:
lined
'having been given material backing?' is the definition.
I can't judge whether this defines the answer.
'been given material backing?' is the wordplay.
'been' becomes 'led' (leading is a kind of being).
'given' means one lot of letters goes inside another.
'material backing?' becomes 'in' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'led' enclosing 'in' is 'LINED'.
Can you help me to learn more?
(Other definitions for lined that I've seen before include "Covered inside" , "What ruler did" , "pockets may be so filled?" , "Given an inner covering" , "Wrinkled or with layer of material on inside" .)