Cunning, pursuing sewing equipment for no reason (10)
I believe the answer is:
needlessly
'equipment for no reason' is the definition.
I can't tell whether this defines the answer.
'cunning pursuing sewing' is the wordplay.
'cunning' becomes 'sly' (synonyms).
'pursuing' says to put letters next to each other.
'sewing' becomes 'needles' (I am not sure about this - if you are sure you should believe this answer much more).
'sly' after 'needles' is 'NEEDLESSLY'.
Can you help me to learn more?
(Other definitions for needlessly that I've seen before include "without good reason" , "without any necessity" , "Unnecessarily" , "without justification" .)