Plant, in retrospect, had trouble making a return (6)
I believe the answer is:
dahlia
'plant' is the definition.
(dahlia is a kind of plant)
'in retrospect had trouble making a return' is the wordplay.
'in retrospect' shows that the letters should be reversed in order (in retrospect means looking back).
'trouble making' becomes 'ail' (I can't justify this - if you can you should believe this answer much more).
'a return' shows that the letters should be reversed in order.
'had' backwards is 'dah'.
'ail' in reverse letter order is 'lia'.
'dah'+'lia'='DAHLIA'
Can you help me to learn more?
(Other definitions for dahlia that I've seen before include "Showy flower from Mexico" , "Lia had a showy flower" , "Flower genus" , "conspicuous bloomer" , "Garden plant with large brightly-coloured flowers" .)