Obsession of a man to get a first-class return (5)
I believe the answer is:
mania
'obsession' is the definition.
(I've seen this in another clue)
'a man to get a first-class return' is the wordplay.
'a man' becomes 'nam' (I can't justify this - if you can you should give a lot more credence to this answer).
'to get' says to put letters next to each other.
'a first class' becomes 'ai' (An - top quality).
'return' says the letters should be written in reverse.
'nam' after 'ai' is 'ainam'.
'ainam' written backwards gives 'MANIA'.
'of' acts as a link.
Can you help me to learn more?
(Other definitions for mania that I've seen before include "fixation" , "Frenzy" , "Craze; overexcitement" , "Mental disorder that results in excessive or violent responses" , "wildness" .)