Bishop discovered card game on vacation - perhaps pontoon (5)
I believe the answer is:
barge
'perhaps pontoon' is the definition.
(I know that pontoon is a type of barge)
'bishop discovered card game on vacation' is the wordplay.
'bishop' becomes 'B' (chess abbreviation).
'discovered' says to take the centre (dis-covered - outer letters removed).
'on vacation' means to remove the middle letters (after the inside letters have vacated the word).
The centre of 'card' is 'ar'.
'game' with its centre taken out is 'ge'.
'b'+'ar'+'ge'='BARGE'
(Other definitions for barge that I've seen before include "Shove - canal boat" , "force" , "Cargo vessel" , "Freight vessel" , "Canal-boat" .)