Delay beginning to seem unlikely (5)
I believe the answer is:
stall
'delay' is the definition.
(stalling is a kind of delaying)
'beginning to seem unlikely' is the wordplay.
'beginning to' suggests taking the first letters.
'unlikely' becomes 'tall' (I've seen this in other clues).
The first letter of 'seem' is 's'.
's'+'tall'='STALL'
(Other definitions for stall that I've seen before include "Commercial booth" , "Theatre seat" , "Hedge" , "Market stand; delay" , "Equivocate" .)