Place to learn mawkishness, a thing of legend (7)
I believe the answer is:
unicorn
'a thing of legend' is the definition.
'place to learn mawkishness' is the wordplay.
'place to learn' becomes 'uni'.
'mawkishness' becomes 'corn' (corn can corniness).
'uni'+'corn'='UNICORN'
(Other definitions for unicorn that I've seen before include "Animal rumoured" , "Imaginary white horse with long horn" , "Legendary one-horned horse" , "Imaginary creature with one horn" , "that's fabulous" .)