Fellow with line in excellent restraint (7)
I believe the answer is:
Here is my best explanation:
'restraint' is the definition.
(manacle is a kind of restraint)
'fellow with line in excellent' is the subsidiary indication.
'fellow' becomes 'man' (I've seen this before**).
'with' is a charade indicator (letters next to each other).
'line' becomes 'l'.
'in' indicates putting letters inside.
'excellent' becomes 'ace' (I've seen this in other clues).
'l' placed inside 'ace' is 'acle'.
(Other definitions for manacle that I've seen before include "Fetter", "Curb", "restricting at the cuff?", "Shackle on the wrist", "Handcuff", "item restricting movement", "Hand/ankle restraint" and "Metal shackle".)