A hot form of curse (4)
I believe the answer is:
oath
'curse' is the definition.
(I know that curse can be written as oath)
'a hot form' is the wordplay.
'form' indicates anagramming the letters.
'a'+'hot'='ahot'
'ahot' is an anagram of 'OATH'.
'of' is the link.
(Other definitions for oath that I've seen before include "Vow, sworn word" , "darn, for example" , "word intended?" , "exasperated comment" , "gadzooks!" .)