Having a lot to learn about colour (5)
I believe the answer is:
green
'colour' is the definition.
(I know this)
'having a lot to learn about' is the wordplay.
I cannot really understand how this works, but
'about' could be 're' ('re' means regarding or about) and 're' is found within the answer.
The remaining letters 'gen' is a valid word which might be clued in a way I don't understand.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for green that I've seen before include "Village space" , "The colour of envy" , ""Go" signal" , "one of eighteen" , "Consultative document" .)