Poles, see, at infrequent intervals (8)
I believe the answer is:
sparsely
'infrequent intervals' is the definition.
(I've seen this before)
'poles see' is the wordplay.
'poles' becomes 'spars ' (spar is a kind of pole).
'see' becomes 'ely' (see is a place with a cathedral - e.g. Ely).
'spars'+'ely'='SPARSELY'
'at' is the link.
(Other definitions for sparsely that I've seen before include "infrequent intervals" , "sporadic distribution" , "Scarcely" , "Thinly (scattered)" , "Meagrely, scantily" .)