Inquiring into return of tool for cutting and excavating (9)
I believe the answer is:
examining
'inquiring into' is the definition.
('examine' can be a synonym of 'inquire into')
'return of tool for cutting and excavating' is the wordplay.
'return of' is a reversal indicator.
'tool for cutting' becomes 'axe'.
'and' is a charade indicator (letters next to each other).
'excavating' becomes 'mining' (I've seen this before).
'axe' back-to-front is 'exa'.
'exa'+'mining'='EXAMINING'
(Other definitions for examining that I've seen before include "Checking out" , "Subjecting to inspection" , "Inquiring into" , "Thoroughly inspecting" , "exploring" .)