Tire following delay (4)
I believe the answer is:
flag
'tire' is the definition.
(I've seen this in another clue)
'following delay' is the wordplay.
'following' becomes 'f' (used when citing page numbers etc).
'delay' becomes 'lag' (lag is a kind of delay).
'f'+'lag'='FLAG'
(Other definitions for flag that I've seen before include "appears to lose energy" , "slow down" , "Item of bunting" , "sink" , "Iris -- become weary" .)