Class muddled three Rs with teenage instructor (14)
I believe the answer is:
kindergartener
'instructor' is the definition.
I know nothing about this answer so I can't judge whether it can be defined by this definition.
'class muddled three rs with teenage' is the wordplay.
'three rs' means three replacements for 'r'.
'class' becomes 'kind' (I've seen this in another clue).
'muddled' is an anagram indicator.
'with' says to put letters next to each other.
'r'+'r'+'r'='rrr'
'rrr' put after 'teenage' is 'teenagerrr'.
'teenagerrr' is an anagram of 'ergartener'.
'kind'+'ergartener'='KINDERGARTENER'
Can you help me to learn more?
(Another definition for kindergartener that I've seen is " young learner?".)