Horse no-one backed after delay (8)
I believe the answer is:
stallion
'horse' is the definition.
(thesaurus)
'no-one backed after delay' is the wordplay.
'one' becomes 'i' (Roman numeral).
'backed' is a reversal indicator.
'after' says to put letters next to each other.
'delay' becomes 'stall' (stalling is a kind of delaying).
'no'+'i'='noi'
'noi' written backwards gives 'ion'.
'ion' put after 'stall' is 'STALLION'.
(Other definitions for stallion that I've seen before include "Male horse, often used for breeding" , "Mare's mate" , "Uncastrated adult male horse" , "Male steed" , "Mount" .)