Reportedly pinch an alloy (5)
I believe the answer is:
steel
'an alloy' is the definition.
(I know that steel is a type of alloy)
'reportedly pinch' is the wordplay.
'reportedly' indicates a 'sounds like' (homophone) clue.
'pinch' becomes 'steal' (I've seen this before).
'steal' sounds like 'STEEL'.
(Other definitions for steel that I've seen before include "Structural metal alloy" , "Knife-sharpener" , "Hard, strong, grey alloy" , "Hard iron alloy" , "Strong metal" .)