This we can say about yellow underwear? (1-6)
I believe the answer is:
y-fronts
'underwear?' is the definition.
(type of underwear)
'this we can say about yellow' is the wordplay.
I cannot quite see how this works, but
'about' could be 'on' (as in a book 'on' a certain topic) and 'on' is located in the answer.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for y-fronts that I've seen before include "Men's underwear" , "Underwear (of a certain character?)" , "Type of underpants" , "Male undergarment" , "Item of male underwear" .)