Selfish spoilsport to prepare trap — those people infuriate (3,2,3,6)
I believe the answer is:
dog in the manger
'selfish spoilsport' is the definition.
'dog in the manger' can be an answer for 'spoilsport' (I've seen this before). I am not certain of the 'selfish' bit.
'prepare trap those people infuriate' is the wordplay.
'prepare' becomes 'do' (I've seen this in other clues).
'trap' becomes 'gin' (gin trap is a kind of animal trap).
'those people' becomes 'them' ('they' refers to a group of people).
'infuriate' becomes 'anger' (I've seen this in another clue).
'do'+'gin'+'them'+'anger'='DOG-IN-THE-MANGER'
'to' is the link.
Can you help me to learn more?
(Other definitions for dog in the manger that I've seen before include "that could disrupt nativity play" , "Selfish person" , "party-pooper?" , "One not letting others use what they themselves have no use for" , "Spoilsport" .)