Eggs on lamb meat? Use only occasionally! (5)
I believe the answer is:
abets
'eggs on' is the definition.
(I've seen this in another clue)
'lamb meat? use only occasionally' is the wordplay.
'only occasionally' means one should take alternating letters (letters taken at regular intervals or occasions).
'lamb'+'meat'+'use'='lambmeatuse'
The alternate letters of 'lambmeatuse' are 'ABETS'.
(Other definitions for abets that I've seen before include "Assists in crime" , "Gives support" , "Assists in wrongdoing" , "Helps (someone to commit crime)" , "Assists or encourages" .)