Touch upon parapet in battle (9)
I believe the answer is:
appertain
'touch' is the definition.
The answer and definition can be both to do with fundamental existence as well as being verbs in their base form.
Perhaps they are linked in a way I don't understand?
'parapet in battle' is the wordplay.
'parapet in' can be anagrammed to 'APPERTAIN'.
But, I'm not clear how this is indicated.
'upon' acts as a link.
Can you help me to learn more?
(Other definitions for appertain that I've seen before include "Bear on" , "Be relevant to" , "Concern" , "Belong, relate (to)" .)