Proust's character is weak, going in opposite directions (5)
I believe the answer is:
swann
'proust's character' is the definition.
(Charles Swann in novels by Marcel Proust)
'weak going in opposite directions' is the wordplay.
'weak' becomes 'wan' (similar in meaning).
'going in' is an insertion indicator.
'opposite directions' becomes 'SN' (opposite compass points).
'wan' inserted within 'sn' is 'SWANN'.
'is' acts as a link.
(Other definitions for swann that I've seen before include "Proust hero" , "Donald - - , composer" , "Proust character" .)