The two answers to this flat are close homophones.

An arrogant fellow named Ben
Was touring in Uruguay when
The vain, _ _ _ _ _ _ _ gent
Vanished in the _ _ _ _ _ _.
Was he missed? At the most, now and
   then.

HINT:
The vain, p _ _ _ _ _ _  gent
Vanished in the P_ _ _ _ _

Answers:

pompous
Pampas 

Credit:
The Enigma 
June, 2020
A. CHEMEM