First? I will occupy that position! (6)
I believe the answer is:
egoist
'will occupy that position' is the definition.
Although both the answer and definition are singular nouns, I cannot understand how they can define each other.
'first? i' is the wordplay.
I cannot quite understand how this works, but
'first?' could be 'ist' (ist resembles 1st) and 'ist' is found within the answer.
'i' could be 'ego' ('I' in Latin) and 'ego' is found within the answer.
No letters remain.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for egoist that I've seen before include "Person with very a good opinion of himself" , "Bighead" , "Excessively conceited person" , "Selfish person" , "number one fan" .)