Words of condolence may be expensive, darling (4,4)
I believe the answer is:
dear dear
'words of condolence may' is the definition.
I know nothing about this answer so I can't judge whether it can be defined by this definition.
'expensive darling' is the wordplay.
'expensive' becomes 'dear' (similar in meaning).
'darling' becomes 'dear' (synonyms).
'dear'+'dear'='DEAR DEAR'
'be' is the link.
Can you help me to learn more?
(Other definitions for dear dear that I've seen before include "Expression of dismay" , "That's a pity!" , "Too bad!" .)