Long sharp object allowed this to be toasted in fire (7)
I believe the answer is:
pikelet
'this to be toasted in fire' is the definition.
The definition suggests a singular noun which matches the answer.
'long sharp object allowed' is the wordplay.
'long sharp object' becomes 'pike' (I can't justify this - if you can you should give a lot more credence to this answer).
'allowed' becomes 'let' (I've seen this before).
'pike'+'let'='PIKELET'
Can you help me to learn more?
(Other definitions for pikelet that I've seen before include "Thin kind of crumpet" , "local crumpet" , "Type of crumpet" , "afternoon treat, perhaps" , "15 [TEACAKE]" .)