Poles are setting trap (5)
I believe the answer is:
snare
'trap' is the definition.
(I know that trap can be written as snare)
'poles are' is the wordplay.
'poles' becomes 'sn' (North and South poles).
'sn'+'are'='SNARE'
'setting' acts as a link.
(Other definitions for snare that I've seen before include "Trap or entangle" , "Lure or trap" , "Kind of trap, often with noose" , "Entrap" , "Trap; type of drum" .)