First knots aligned (7)
I believe the answer is:
leading
'first' is the definition.
(leading can mean first or main)
'knots aligned' is the wordplay.
'knots' is an anagram indicator (I've seen 'knot' mean this (letters are tangled up)).
'aligned' with letters rearranged gives 'LEADING'.
(Other definitions for leading that I've seen before include "In the chair" , "'Showing the way, out in front (7)'" , "Aligned in front" , "Prominent" , "Foremost" .)