Rubies, if not set properly, can result in injury (6)
I believe the answer is:
bruise
'injury' is the definition.
(I know that bruise is a type of injury)
'rubies if not set properly can result' is the wordplay.
'rubies' anagrams to 'BRUISE'.
However, I'm not sure how this is indicated.
'in' is the link.
Can you help me to learn more?
(Other definitions for bruise that I've seen before include "Injure underlying soft tissue or bone" , "Sign of injury" , "Mark left by blow" , "Discoloured injury" , "Injury mark; sounds like ferments" .)