Time to regret being honest (4)
I believe the answer is:
true
'honest' is the definition.
(I've seen this before)
'time to regret' is the wordplay.
'time' becomes 't'.
'to regret' becomes 'rue' ('rue' can be a synonym of 'regret').
't'+'rue'='TRUE'
'being' acts as a link.
(Other definitions for true that I've seen before include "comfortable" , "Exact; faithful" , "Factually correct" , "Genuine, actual" , "Factually accurate" .)