Best end to introduce spinner (6)
I believe the answer is:
tiptop
'best' is the definition.
(tiptop means excellent or high-quality)
'end to introduce spinner' is the wordplay.
'end' becomes 'tip' (tip is a kind of end).
'to introduce' means one lot of letters go next to another (some letters come before or introduce others).
'spinner' becomes 'top' (a spinning top).
'tip'+'top'='TIPTOP'
(Other definitions for tiptop that I've seen before include "First-class" , "The pinnacle of perfection" , "Very fine" , "The very highest point" , "The height of excellence" .)