Personal reason for involvement in underwear? (6,8)
I believe the answer is:
vested interest
'underwear?' is the definition.
Although both the answer and definition are singular nouns, I don't see how they can define each other.
'personal reason for involvement' is the wordplay.
'personal reason for' becomes 'vested' (I can't explain this - if you can you should believe this answer much more).
'involvement' becomes 'interest' (synonyms).
'vested'+'interest'='VESTED INTEREST'
'in' is the link.
Can you help me to learn more?
(Other definitions for vested interest that I've seen before include "Personal stake in an undertaking" , "It could be good for you!" , "Having personal concern" .)