Yes, it sounds like the first person (3)
I believe the answer is:
aye
'yes' is the definition.
(I've seen this before)
'it sounds like the first person' is the wordplay.
'it sounds like' indicates a 'sounds like' (homophone) clue.
'the first person' becomes 'I' ('I' is a first-person pronoun).
'i' sounds like 'AYE'.
(Other definitions for aye that I've seen before include "Yes (archaic)" , "An affirmative vote" , "One voting in favour" , "Yes, at the double for the sailor" , "Yes vote" .)