Ran round bend turning up for fight (4)
I believe the answer is:
duel
'for fight' is the definition.
(duel is a kind of fight)
'ran round bend turning up' is the wordplay.
'ran' becomes 'led' ('lead' can be a synonym of 'run').
'round' means one lot of letters goes inside another.
'bend' becomes 'U' (a U-bend is a kind of bend - pipe under sink).
'turning up' says the letters should be written in reverse.
'led' going around 'u' is 'leud'.
'leud' written backwards gives 'DUEL'.
(Other definitions for duel that I've seen before include "Contest between two with deadly weapons" , "honourable affair" , "Gentlemen's disagreement" , "Fight between two persons" , "Fight to the death between two people" .)