Out of practice in game with pen (5)
I believe the answer is:
rusty
'out of practice' is the definition.
(I've seen this before)
'game with pen' is the wordplay.
'game' becomes 'ru' (rugby union).
'with' says to put letters next to each other.
'pen' becomes 'sty' (sty is a kind of pen).
'ru'+'sty'='RUSTY'
'in' is the link.
(Other definitions for rusty that I've seen before include "(Of iron) affected by damp" , "(Of knowledge) not current" , "Stiff with age" , "(Of iron) corroded" , "Reddish," .)