Red card: did moan after fouling (7)
I believe the answer is:
diamond
'red card' is the definition.
(I've seen this before)
'did moan after fouling' is the wordplay.
'after' says to put letters next to each other.
'fouling' is an anagram indicator (I've seen 'foul' mean this).
'did'+'moan'='didmoan'
'didmoan' anagrammed gives 'DIAMOND'.
(Other definitions for diamond that I've seen before include "(Usually colourless) gemstone - card" , "Playing card - baseball playing-field" , "nickname of US State" , "Form of carbon" , "Precious stone for mad Odin" .)