Sources of pain to employ in crimes (7)
I believe the answer is:
sinuses
'sources of pain' is the definition.
Although both the answer and definition are plural nouns, I don't understand how they can define each other.
'employ in crimes' is the wordplay.
'employ' becomes 'use' (synonyms).
'in' is an insertion indicator.
'crimes' becomes 'sins'.
'use' put into 'sins' is 'SINUSES'.
'to' is the link.
Can you help me to learn more?
(Other definitions for sinuses that I've seen before include "holes in the head" , "Top spaces" , "Cavities in skull connecting with nostrils" , "Empty spaces" .)