Flynn acted right heartily in a new role (5)
I believe the answer is:
errol
'flynn' is the definition.
(I've seen this before)
'acted right heartily in a new role' is the wordplay.
'acted right heartily' becomes 'r' (I can't justify this - if you can you should give a lot more credence to this answer).
'in' means one lot of letters goes inside another.
'a new' indicates an anagram.
'role' is an anagram of 'erol'.
'r' going inside 'erol' is 'ERROL'.
Can you help me to learn more?
(Other definitions for errol that I've seen before include "Old film star" , "- Flynn, twentieth century film actor" , "-- Flynn, Hollywood actor" , "- - Flynn, film star" , "- Flynn, US film actor" .)