Sent off for traps (4)
I believe the answer is:
nets
'traps' is the definition.
(net is a kind of trap)
'sent off' is the wordplay.
'off' indicates an anagram.
'sent' is an anagram of 'NETS'.
'for' acts as a link.
(Other definitions for nets that I've seen before include "'Traps for 29 dn, say (4)'" , "practice area" , "puts ball into goal" , "Captures" , "Traps, to catch fish say" .)