Having come back, worked regularly at again (7)
I believe the answer is:
replied
'having come back' is the definition.
I can't tell whether this defines the answer.
'worked regularly at again' is the wordplay.
'worked regularly' becomes 'plied' (to ply is to work with a tool. I am not sure about the 'regularly' bit.).
'at' is a charade indicator (letters next to each other) (I've seen this in other clues).
'again' becomes 're' (prefix meaning 'again').
'plied' after 're' is 'REPLIED'.
Can you help me to learn more?
(Other definitions for replied that I've seen before include "Responded" , "Answered back" , "Wrote back" , "Gave answer" , "came back" .)