Many an iron worker, apparently, is under age! (5)
I believe the answer is:
minor
'many an' is the definition.
Both the definition and answer are adjectives. Perhaps they are linked in a way I don't understand?
'iron worker apparently is under age' is the wordplay.
I cannot quite see how this works, but
an anagram of 'iron' is 'inor' which is present in the answer.
A single letter 'm' remains which might be clued in a way I don't see.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for minor that I've seen before include "Young person below voting age" , "Morris car; tending to melancholy (mus.)" , "One not yet of legal age" , "Junior" , "One hasn't reached legal majority" .)