Initially right in hand (5)
I believe the answer is:
first
'initially' is the definition.
(thesaurus)
'right in hand' is the wordplay.
'right' becomes 'r' (common abbreviation).
'in' means one lot of letters goes inside another.
'hand' becomes 'fist' (fist is a kind of hand).
'r' put into 'fist' is 'FIRST'.
(Other definitions for first that I've seen before include "Most important" , "Position for gold" , "second to none" , "Rifts of supreme sort" , "Rifts (anag)" .)