Fight a law-breaker on British Rail (5)
I believe the answer is:
brawl
'fight' is the definition.
(brawl is a kind of fight)
'a law-breaker on british rail' is the wordplay.
'a law breaker' becomes 'awl' (I can't explain this - if you can you should give a lot more credence to this answer).
'on' means one lot of letters go next to another.
'british rail' becomes 'br'.
'awl' after 'br' is 'BRAWL'.
Can you help me to learn more?
(Other definitions for brawl that I've seen before include "dispute" , "Quarrel noisily" , "Public punch-up" , "Abounding" , "Scuffle, unseemly fight" .)