Send unsolicited plans back (4)
I believe the answer is:
spam
'send unsolicited' is the definition.
I can't judge whether this defines the answer.
'plans back' is the wordplay.
'plans' becomes 'maps' (I've seen this in another clue).
'back' shows that the letters should be reversed in order.
'maps' backwards is 'SPAM'.
Can you help me to learn more?
(Other definitions for spam that I've seen before include "Junk email" , "unwanted correspondence" , "Tinned meat made largely from pork" , "Unwanted communication" , "Send unsolicited mail" .)