Mentioned being sorry about faint heartedness (4)
I believe the answer is:
said
'mentioned' is the definition.
(I've seen this before)
'sorry about faint heartedness' is the wordplay.
I cannot really see how this works, but
'about' could be 'a' (abbreviation in Chambers) and 'a' is found in the answer.
The remaining letters 'sid' is a valid word which might be clued in a way I don't see.
This explanation may well be incorrect...
'being' is the link.
Can you help me to learn more?
(Other definitions for said that I've seen before include "Uttered at Suez port" , "Stated" , "Spoke" , "Rumoured" , "put in speech" .)