Proceed first for the self! (6)
I believe the answer is:
forego
'proceed' is the definition.
The definition and answer can be both to do with fundamental existence as well as being verbs in their base form.
Maybe they are linked in a way I don't understand?
'first for the self' is the wordplay.
'first' means one lot of letters go next to another.
'the self' becomes 'ego' ('ego' can be a synonym of 'self').
'for'+'ego' is 'FOREGO'.
Can you help me to learn more?
(Other definitions for forego that I've seen before include "Precede (in place/time)" , "Surrender" , "Go without (desirable thing)" , "Go without (something desirable)" , "Get ahead" .)