Hangs fire as heat is set off the wall (9)
I believe the answer is:
hesitates
'hangs fire' is the definition.
The answer and definition can be both to do with fundamental existence as well as being verbs in their -s form.
Perhaps they are linked in a way I don't understand?
'heat is set off the wall' is the wordplay.
'set off' is an anagram indicator.
'the wall' becomes 'tes' (I am not sure about this - if you are sure you should believe this answer much more).
'heat'+'is'='heatis'
'heatis' is an anagram of 'hesita'.
'hesita'+'tes'='HESITATES'
'as' acts as a link.
Can you help me to learn more?
(Other definitions for hesitates that I've seen before include "Has misgivings" , "dithers" , "Is somewhat lost for words" , "rather dubious" , "thinks twice" .)