Harold joins fellow admiral in hold (4,6)
I believe the answer is:
half nelson
'hold' is the definition.
(I know that half nelson is a type of nelson)
'harold joins fellow admiral' is the wordplay.
'harold' becomes 'Hal' (diminutive, as in Hal Prince).
'joins' is a charade indicator (letters next to each other).
'fellow' becomes 'F' (abbreviation - of a society etc.).
'admiral' becomes 'nelson' (I've seen this before).
'hal'+'f'+'nelson'='HALF-NELSON'
'in' is the link.
(Other definitions for half nelson that I've seen before include "a description of what can be seen from the side of Trafalgar Square?" , "Wrestling hold" .)