Painter's common requirement: more blue about the pupil's edges (10)
I believe the answer is:
stepladder
'painter's common requirement' is the definition.
I can't judge whether this defines the answer.
'more blue about the pupil's edges' is the wordplay.
'more blue' becomes 'sadder' ('sad' can be similar in meaning to 'blue').
'about' means one lot of letters goes inside another.
'the pupil's edges' becomes 'tepl' (I can't justify this - if you can you should give a lot more credence to this answer).
'sadder' going around 'tepl' is 'STEPLADDER'.
Can you help me to learn more?
(Other definitions for stepladder that I've seen before include "piece of equipment" , "Portable climbing aid" , "Portable means of ascent" , "Painter's mate" , "Domestic climbing aid" .)