If young, you can't beat this papaya gel -- I'm itching to sample (3,5)
I believe the answer is:
age limit
'if young you can't beat this' is the definition.
The definition suggests a singular noun which matches the answer.
'papaya gel i'm itching to sample' is the wordplay.
'to sample' indicates a hidden word (I've seen 'sampled' mean this (I've seen this in other clues)).
'AGE LIMIT' is hidden within 'papaya gel im itching'.
Can you help me to learn more?
(Other definitions for age limit that I've seen before include "Regulation based on year of birth that sets down when one can no longer do something" , "Maturity restriction" , "Regulation regarding length of time one has lived" , "Bar to those too old or too young" , "I am legit (anag)" .)