A wrench, just when the pair's got a break point (6)
I believe the answer is:
sprain
'a wrench' is the definition.
(I know that sprain is a type of wrench)
'when the pair's got a break point' is the wordplay.
'when' becomes 'si' (I can't justify this - if you can you should believe this answer much more).
'the pair' becomes 'pr' (abbreviation).
'got' says to put letters next to each other.
'break' indicates putting letters inside (inserted letters break into the word).
'point' becomes 'n' (North).
'pr'+'a'='pra'
'si' placed around 'pra' is 'sprai'.
'sprai'+'n'='SPRAIN'
'just' acts as a link.
Can you help me to learn more?
(Other definitions for sprain that I've seen before include "Twist ligament(s)" , "Injure a joint by twisting its ligaments" , "Slight muscle injury, eg to ankle" , "Muscle injury caused by wrench." , "Turn" .)