Swap made at start of capital card game (4)
I believe the answer is:
solo
'card game' is the definition.
(I've seen this before)
'swap made at start of capital' is the wordplay.
'swap' says to put letters next to each other.
'made at' becomes 'lo' (I am not sure about this - if you are sure you should believe this answer much more).
'capital' suggests taking the first letters.
The initial letters of 'start of' is 'so'.
'lo' put after 'so' is 'SOLO'.
(Other definitions for solo that I've seen before include "Piece for single performer" , "Fly aircraft" , "(Piece performed) on one's own" , "Done by one person" , "One-person performance" .)