Possibly saw Rob in retirement (4)
I believe the answer is:
tool
'possibly saw' is the definition.
(I know that power saw is a type of power tool)
'rob in retirement' is the wordplay.
'rob' becomes 'loot' (loot can mean to rob).
'in retirement' is a reversal indicator (retire can mean to go back or backwards).
'loot' written backwards gives 'TOOL'.
(Other definitions for tool that I've seen before include "Implement - agency" , "Practical implement" , "Instrument, implement" , "Appliance" , "Working instrument" .)