Mustn't steal total amount - that would be incendiary (3)
I believe the answer is:
tnt
'incendiary' is the definition.
The definition and answer can be both man-made objects as well as being singular nouns.
Perhaps they are linked in a way I don't understand?
'mustn't steal total amount' is the wordplay.
'steal' is a deletion indicator.
'total amount' becomes 'sum' (I've seen this in another clue).
'mustnt' with 'sum' taken away is 'TNT'.
'that would be' is the link.
Can you help me to learn more?
(Other definitions for tnt that I've seen before include "Type of high explosive" , "Explosive stuff" , "Initially, powerful explosive" , "Very powerful explosive, compressed" , "Explosive compound" .)