Card game done naked finished outside (7)
I believe the answer is:
diamond
'card' is the definition.
(diamond is a kind of card)
'game done naked finished outside' is the wordplay.
'game' becomes 'am' (I can't explain this - if you can you should believe this answer much more).
'naked' indicates the central letters.
'finished' becomes 'did'.
'outside' indicates putting letters inside.
The central letters of 'done' are 'on'.
'am'+'on'='amon'
'amon' inserted inside 'did' is 'DIAMOND'.
(Other definitions for diamond that I've seen before include "American field" , "Gemstone - baseball field" , "Carbon gemstone" , "Hard precious stone" , "Something precious" .)