Stable with one working horse (8)
I believe the answer is:
stallion
'horse' is the definition.
(thesaurus)
'stable with one working' is the wordplay.
'stable' becomes 'stall' (I've seen this in other clues).
'with' says to put letters next to each other.
'one' becomes 'i' (Roman numeral).
'working' becomes 'on'.
'stall'+'i'+'on'='STALLION'
(Other definitions for stallion that I've seen before include "Male horse, often used for breeding" , "Male steed" , "Stud" , "Male horse kept for breeding" , "Uncastrated adult male horse" .)