Colour returns to a learner in a tree (5)
I believe the answer is:
alder
'tree' is the definition.
(I know that alder is a type of tree)
'colour returns to a learner' is the wordplay.
'colour' becomes 'red' (red is a kind of colour).
'returns' is a reversal indicator.
'to' says to put letters next to each other (I've seen this in other clues).
'learner' becomes 'l' (as in a learner driver with L-plates on their car).
'red' written backwards gives 'der'.
'a'+'l'='al'
'der' put after 'al' is 'ALDER'.
'in a' acts as a link.
(Other definitions for alder that I've seen before include "Forward movement" , "A tree for Adler" , "Tree growing in damp ground" , "Shrub or tree with cone-like fruits" , "Tree related to the birch" .)