One teetotal in party? The same again! (5)
I believe the answer is:
ditto
'same again' is the definition.
(the same as previously mentioned)
'one teetotal in party?' is the wordplay.
'one teetotal' becomes 'tt' (abbreviation).
'in' indicates putting letters inside.
'party?' becomes 'dio' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'tt' inserted into 'dio' is 'DITTO'.
'the' acts as a link.
(Other definitions for ditto that I've seen before include "Do alternative" , "Likewise" , "Mark used to indicate repetition" , "that which has been said" , "Two dots indicating the same again" .)