Understand criminal's regret accepting time (8)
I believe the answer is:
construe
'understand' is the definition.
(construing is a kind of understanding)
'criminal's regret accepting time' is the wordplay.
'criminal's' becomes 'cons' (abbreviation for 'convict').
'regret' becomes 'rue' ('rue' can be a synonym of 'regret').
'accepting' means one lot of letters goes inside another.
'time' becomes 't'.
'cons'+'rue'='consrue'
'consrue' enclosing 't' is 'CONSTRUE'.
(Other definitions for construe that I've seen before include "Read - trounces (anag)" , "Translate" , "Analyse language" , "Counters (anag) - interpret" , "Analyse syntax using counters" .)