Bore's degree of suitability (7)
I believe the answer is:
calibre
This might be a double definition.
'bore's' is the first definition.
(gun terminology)
'degree of suitability' is the second definition.
'calibre' can be an answer for 'degree' (calibre is a kind of degree). I am unsure of the 'of suitability' bit.
Can you help me to learn more?
(Other definitions for calibre that I've seen before include "Bullet size" , "bore on the Tube?" , "gifts" , "Quality - gun barrel bore" , "Quality of character" .)