Skilled worker is irregular, not punctual at first (7)
I believe the answer is:
artisan
'skilled worker' is the definition.
(an artisan is a skilled craftsperson)
'is irregular not punctual at first' is the wordplay.
I cannot really see how this works, but
'is' is found in the answer.
'first' could be 'a' (first letter of the alphabet) and 'a' is present in the answer.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for artisan that I've seen before include "Skilled manual 17" , "Handy worker" , "Skilled tradesman" , "Smith" , "Skilled worker at craft or trade" .)