Correct height on masts, sails, etc (5)
I believe the answer is:
right
'correct' is the definition.
(synonyms)
'height on masts sails etc' is the wordplay.
'height' becomes 'ht' (I've seen this in other clues).
'on' says to put letters next to each other.
'masts sails etc' becomes 'rig' (rig is the arrangement of sails etc on a ship).
'ht' after 'rig' is 'RIGHT'.
(Other definitions for right that I've seen before include "Conservative - correct" , "correctly" , "Spot-on" , "Punch" , "Equitable" .)