Warning forward respectfully, this may be tugged (8)
I believe the answer is:
forelock
'respectfully this may be tugged' is the definition.
(tugging a forelock is a sign of respect)
'warning forward' is the wordplay.
'warning' becomes 'fore' (I've seen this before).
'forward' becomes 'lock' (type of rugby forward).
'fore'+'lock'='FORELOCK'
(Other definitions for forelock that I've seen before include "Part of a horse's mane growing forward between the ears" , "It was touched in servility" , "Hairy growth" , "which droops between temples?" , "Piece of hair (tugged in respect)" .)