Typical head on flag (3-8)
I believe the answer is:
bog-standard
'typical head on flag' is the definition.
I don't know anything about this answer so I cannot judge whether this works.
'typical head on flag' is the wordplay.
'typical head' becomes 'bog' (I can't explain this - if you can you should give a lot more credence to this answer).
'on' is a charade indicator (letters next to each other) (in a down clue, letters appear on others).
'flag' becomes 'standard' (standard is a kind of flag).
'bog'+'standard'='BOG-STANDARD'
Can you help me to learn more?
(Other definitions for bog-standard that I've seen before include "Everyday" , "Utterly ordinary" , "Run-of-the-mill" , "Basic -- ordinary (slang)" .)