Sponsor honourable man keeping up party standard (9)
I believe the answer is:
godparent
'sponsor' is the definition.
(I know that godparent is a type of sponsor)
'honourable man keeping up party standard' is the wordplay.
'honourable man' becomes 'gent' (I've seen this before).
'keeping' means one lot of letters goes inside another (some letters kept inside).
'up' says the letters should be written backwards (in down clue: letters go upwards).
'party' becomes 'do' (do is a kind of party).
'standard' becomes 'par' (standard of play in golf).
'do' reversed gives 'od'.
'od'+'par'='odpar'
'gent' placed around 'odpar' is 'GODPARENT'.
(Other definitions for godparent that I've seen before include "as one responsible for charge" , "Pet dragon (anag)" , "Baptism sponsor" , "Religious guardian" .)