Labour opponents knock back housing article (9)
I believe the answer is:
endeavour
'labour' is the definition.
(endeavour can mean a labour or effort)
'opponents knock back housing article' is the wordplay.
'opponents' becomes 'EN' (East and North players in the card game bridge).
'knock back' becomes 'devour' (both can mean to eat).
'housing' indicates putting letters inside.
'article' becomes 'a' (English indefinite article).
'devour' placed around 'a' is 'deavour'.
'en'+'deavour'='ENDEAVOUR'
(Other definitions for endeavour that I've seen before include "Cook's old vessel" , "Expenditure of effort" , "Make a serious effort" , "Try - Captain Cook's vessel" , "Aim" .)