Poor colt's terrible form (8)
I believe the answer is:
protocol
'form' is the definition.
(I've seen this before)
'poor colt's terrible' is the wordplay.
'terrible' indicates anagramming the letters.
'poor'+'colt'='poorcolt'
'poorcolt' anagrammed gives 'PROTOCOL'.
(Other definitions for protocol that I've seen before include "Official code of procedure" , "Formalities" , "customs" , "Rules of conduct" , "Draft treaty" .)