The house maid, Mai, went off to get fish (3)
I believe the answer is:
cod
'fish' is the definition.
(type of fish)
'the house maid mai went' is the wordplay.
'the house' becomes 'co' (I've seen this in other clues).
'went' is a deletion indicator (selected letters go away).
'maid' with 'mai' taken away is 'd'.
'co'+'d'='COD'
'off to get' is the link.
I am not very happy about this link. Some or all of it may be part of another bit of the clue.
Can you help me to learn more?
(Other definitions for cod that I've seen before include "catch!" , "Cash on delivery, in short, for this fish" , "method of payment" , "Fish noted for liver oil" , "A fish; a hoax (slang)" .)