Have a go at and complain - it's a British tradition (5,4)
I believe the answer is:
roast beef
'a british tradition' is the definition.
Although both the answer and definition are singular nouns, I cannot see how they can define each other.
'have a go at and complain' is the wordplay.
'have a go at' becomes 'roast' (I've seen this before).
'and' means one lot of letters go next to another.
'complain' becomes 'beef' (beefing is a kind of complaining).
'roast'+'beef'='ROAST-BEEF'
'it's' is the link.
Can you help me to learn more?
(Other definitions for roast beef that I've seen before include "Typical English dish" , "Traditional English food" , "Sunday meat?" , "part of lunch for Sun?" , "Traditional English dish" .)