Difference in microns rose (7)
I believe the answer is:
crimson
This clue might be a double definition.
'difference in microns' is the first definition.
'crimson' can be an answer for 'microns' (I have seen 'Microns of colour ' mean 'crimson' so perhaps 'microns' could also mean 'crimson'). I am not sure about the 'difference in' bit.
'rose' is the second definition.
(thesaurus)
Can you help me to learn more?
(Other definitions for crimson that I've seen before include "Vivid red" , "Rich deep red" , "Blood-red" , "Shade of red" , "Ruddy" .)