Social occasion - central bit in backyard? (6,5)
I believe the answer is:
dinner party
'social occasion' is the definition.
(a dinner party is a type of social occasion)
'central bit in backyard?' is the wordplay.
I cannot really see how this works, but
'central' could be 'inner' (similar in meaning) and 'inner' is present in the answer.
'bit' could be 'part' (both can mean a piece of something) and 'part' is found within the answer.
This may be the basis of the clue (or it may be nonsense).
(Other definitions for dinner party that I've seen before include "social function" , "Sociable gathering for meal" , "Social gathering over a meal" .)