Moor who had to return the greeting (7)
I believe the answer is:
othello
'moor who' is the definition.
'othello' can be an answer for 'moor' (I've seen this before). I'm not certain of the remainder of the definition.
'to return the greeting' is the wordplay.
'return' shows that the letters should be reversed in order.
'the greeting' becomes 'hello' (hello is a kind of greeting).
'to' backwards is 'ot'.
'ot'+'hello'='OTHELLO'
'had' is the link.
Can you help me to learn more?
(Other definitions for othello that I've seen before include "Shakespeare hero" , "drama!" , "Shakespeare play set in Venice/Cyprus" , "Literary character" , "Dramatic Moor" .)