Stagger up gripping teetotal character (6)
I believe the answer is:
letter
'character' is the definition.
(letter is a kind of character)
'stagger up gripping teetotal' is the wordplay.
'stagger' becomes 'reel' ('reel' can be a synonym of 'stagger').
'up' says the letters should be written backwards (in down clue: letters go upwards).
'gripping' indicates putting letters inside.
'teetotal' becomes 'tt' (abbreviation).
'reel' back-to-front is 'leer'.
'leer' placed around 'tt' is 'LETTER'.
(Other definitions for letter that I've seen before include "It's one of twenty-six" , "Alphabetic character" , "Character; missive" , "Form of correspondence" , "Character - landlord - epistle" .)