Joe holding king initially reluctant playing card (5)
I believe the answer is:
joker
'playing card' is the definition.
(I've seen this before)
'joe holding king initially reluctant' is the wordplay.
'holding' means one lot of letters goes inside another.
'king' becomes 'K' (chess abbreviation).
'initially' indicates taking the first letters.
The first letter of 'reluctant' is 'r'.
'joe' enclosing 'k' is 'joke'.
'joke'+'r'='JOKER'
(Other definitions for joker that I've seen before include "Playing card" , "Humorist" , "may appear wild in play" , "Wild card" , "Card - wag" .)