Expires, broken by a wager, and disease (8)
I believe the answer is:
diabetes
'disease' is the definition.
(diabetes is a kind of gland disease)
'expires broken by a wager' is the wordplay.
'expires' becomes 'dies' ('die' can be a synonym of 'expire').
'broken by' means one lot of letters goes inside another.
'wager' becomes 'bet' ('bet' can be a synonym of 'wager').
'a'+'bet'='abet'
'dies' going around 'abet' is 'DIABETES'.
'and' acts as a link.
(Other definitions for diabetes that I've seen before include "illness" , "Disorder causing excessive urination" , "Insulin-related disorder" , "Insulin-linked disorder" , "Blood disorder" .)