Grand love affairs, not right, relatively criminal? (8)
I believe the answer is:
bigamous
'relatively criminal?' is the definition.
'grand love affairs not right' is the wordplay.
'grand' becomes 'big'.
'love affairs' becomes 'amours' (I've seen this before).
'not' indicates named letters should be taken away.
'right' becomes 'r' (common abbreviation).
'amours' with 'r' removed is 'amous'.
'big'+'amous'='BIGAMOUS'
(Other definitions for bigamous that I've seen before include "Marrying twice illegally" , "Doubly married" , "Having another other half!" , "Underground cemetery" , "Involving illegal marriage" .)