Down following defeat (5)
I believe the answer is:
floss
'down' is the definition.
(thesaurus)
'following defeat' is the wordplay.
'following' becomes 'f.' (used when citing page numbers etc).
'defeat' becomes 'loss' (I've seen this in another clue).
'f'+'loss'='FLOSS'
(Other definitions for floss that I've seen before include "Teeth-cleaning thread" , "flower in Victorian novel" , "teeth cleaner" , "Eliot's river" , "A mass of silky fibres - dental?" .)