Wise man, inexperienced in colour (4,5)
I believe the answer is:
sage green
'colour' is the definition.
(I know that sage green is a colour)
'wise man inexperienced' is the wordplay.
'wise man' becomes 'sage' (sage is a kind of wise man).
'inexperienced' becomes 'green' (similar in meaning).
'sage'+'green'='SAGE-GREEN'
'in' is the link.
(Other definitions for sage green that I've seen before include "Dull colour" , "Colour of plant" .)