Irish author known initially when working for long time (4)
I believe the answer is:
aeon
'long time' is the definition.
(aeon is a kind of long time)
'irish author known initially when working' is the wordplay.
I cannot quite see how this works, but
'when' could be 'on' (I've seen this in other clues) and 'on' is located in the answer.
The remaining letters 'ae' is a valid word which might be clued in a way I don't see.
This explanation may well be incorrect...
'for' acts as a link.
Can you help me to learn more?
(Other definitions for aeon that I've seen before include "Longest division of geological time" , "Eternity" , "Vast time period" , "Indefinitely long period of time" , "A very long time, an age" .)