More than one clever chap scratching head for hours (4)
I believe the answer is:
ages
'more than one clever chap' is the definition.
I can't tell whether this definition defines the answer.
'scratching head for hours' is the wordplay.
'head' says to take the initial letters.
'for' means one lot of letters go next to another (I've seen this in other clues).
'hours' becomes 'age' (I can't explain this - if you can you should believe this answer much more).
The first letter of 'scratching' is 's'.
's' after 'age' is 'AGES'.
Can you help me to learn more?
(Other definitions for ages that I've seen before include "Aeons" , "Times" , "Sage (anag)" , "Gets older" , "Rock of - - (hymn)" .)