Servant crazy to get out of line (4)
I believe the answer is:
'servant' is the definition.
(I know that maid is a type of servant)
'crazy to get out of line' is the wordplay.
'crazy' becomes 'mad' (synonyms).
'to get' means one lot of letters goes inside another.
'out of line' becomes 'i' (I can't justify this - if you can you should believe this answer much more).
'mad' enclosing 'i' is 'MAID'.
Can you help me to learn more?
(Other definitions for maid that I've seen before include "One in service" , "Female servant - young girl" , "- - -of-all-work" , "Damsel" , "Young woman - servant" .)