Boxer may be one of little importance (11)
I believe the answer is:
lightweight
This clue is a double definition.
'boxer' is the first definition.
(I know that lightweight is a type of boxer)
'one of little importance' is the second definition.
(I've seen this before)
'may be' acts as a link.
(Other definitions for lightweight that I've seen before include "Of little substance" , "of little importance" , "Fighter" , "Carrying little punch?" , "Insubstantial" .)