Longs for time with poles (6)
I believe the answer is:
'longs for' is the definition.
(I've seen this in another clue)
'time with poles' is the wordplay.
'time' becomes 'year' (year is a unit of time).
'with' means one lot of letters go next to another.
'poles' becomes 'NS' (North and South poles).
(Other definitions for yearns that I've seen before include "Longs for, pines" , "'Hankers, longs (6)'" , "'Craves, longs for (6)'" , "Desires strongly" , "Craves, longs intensely" .)