Reputed to be sorry about the faint heart (4)
I believe the answer is:
said
'reputed' is the definition.
(thesaurus)
'sorry about the faint heart' is the wordplay.
'sorry' becomes 'sad' ('sad' can be a synonym of 'sorry'**).
'about' indicates putting letters inside.
'heart' means to look at the middle letters.
The central letter of 'faint' is 'i'.
'sad' going around 'i' is 'SAID'.
'to be' acts as a link.
(Other definitions for said that I've seen before include "Uttered at Suez port" , "Expressed orally" , "put in speech" , "... gave expression" , "Remarked" .)