Is into deep pondering when maltreating (8)
I believe the answer is:
misusing
'maltreating' is the definition.
(I've seen this before)
'is into deep pondering' is the wordplay.
'into' means one lot of letters goes inside another.
'deep pondering' becomes 'musing' (synonyms. I am not sure about the 'deep' bit.).
'is' inserted within 'musing' is 'MISUSING'.
'when' is the link.
Can you help me to learn more?
(Other definitions for misusing that I've seen before include "Maltreating" , "Perverting, misapplying" .)