Clueless character losing head over harangue (8)

I believe the answer is:

ignorant

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'clueless' is the definition.

'character losing head over harangue' is the wordplay.
'character' becomes 'i'.
'losing head over' becomes 'gno' (I can't explain this - if you can you should believe this answer much more).
'harangue' becomes 'rant' (synonyms).
'i'+'gno'+'rant'='IGNORANT'

Can you help me to learn more?

(Other definitions for ignorant that I've seen before include "blissful?" , "Knowing nothing" , "Lacking information" , "Lacking knowledge in Tir na nOg" , "Lacking knowledge or awareness" .)

I've seen this clue in The Telegraph.

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