Having circled both poles, track back (7)
I believe the answer is:
sponsor
'back' is the definition.
(I've seen this before)
'having circled both poles track' is the wordplay.
I cannot really see how this works, but
'poles' could be 'ns' (north and south poles) and 'ns' is located in the answer.
'track' could be 'spoor' (track left by an animal) and 'spoor' is located in the remaining letters.
No letters remain.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for sponsor that I've seen before include "One offering support" , "Financial backer" , "Patron or backer" , "Promoter; funder" , "Provide backing" .)