Airport, it's said, entered by Poles (8)
I believe the answer is:
stansted
'airport' is the definition.
(I've seen this before)
'said entered by poles' is the wordplay.
'said' becomes 'stated' ('state' can be a synonym of 'say').
'entered by' indicates putting letters inside (I've seen this in other clues).
'poles' becomes 'NS' (North and South poles).
'stated' going around 'ns' is 'STANSTED'.
'it's' acts as a link.
(Other definitions for stansted that I've seen before include "Departure point" , "Airport north of London" , "One of London's airports" .)