Supporters turn on United's shambles (5)
I believe the answer is:
snafu
'supporters turn on united's shambles' is the definition.
I can't tell whether this defines the answer.
'supporters turn on united's' is the wordplay.
'supporters' becomes 'fans' (fan is a kind of supporter).
'turn' says the letters should be written backwards.
'on' means one lot of letters go next to another.
'united' becomes 'U' (abbreviation).
'fans' back-to-front is 'snaf'.
'snaf'+'u'='SNAFU'
Can you help me to learn more?
(Other definitions for snafu that I've seen before include "Chaos (US slang)" , "mess as usual" , "a mess of things" , "Bloomer" , "Chaotic situation" .)