Starts to learn all about colour of milk (7)
I believe the answer is:
lacteal
'milk' is the definition.
(thesaurus)
'starts to learn all about colour of' is the wordplay.
'starts to' says to take the initial letters.
'about' becomes 'c' (abbreviation for circa).
'colour of' becomes 'teal' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
The first letters of 'learn all' is 'la'.
'la'+'c'+'teal'='LACTEAL'
Can you help me to learn more?
(Other definitions for lacteal that I've seen before include "Milk-like; pertaining to milk" , "Milky resin" .)