Single sub announced (4)
I believe the answer is:
lone
'single' is the definition.
(synonyms)
'sub announced' is the wordplay.
'sub' becomes 'loan' (British term for advance against income).
'announced' shows a homophone (sound like).
'loan' is a homophone of 'LONE'.
(Other definitions for lone that I've seen before include "Sole" , "Single and isolated" , "He likes to operate by himself" , "Companionless" , "Solitary, sounds like advance" .)