Abundant plunder left out (4)
I believe the answer is:
rife
'abundant' is the definition.
(similar in meaning)
'plunder left out' is the wordplay.
'plunder' becomes 'rifle' (synonyms).
'left' becomes 'L' (common abbreviation).
'out' is a deletion indicator.
'rifle' with 'l' taken out is 'RIFE'.
(Other definitions for rife that I've seen before include "Widespread sort of fire" , "Endemic" , "Of widespread occurrence" , "Abounding" , "Widespread like fire" .)