Secret things drunkard hides in English heather (9)
I believe the answer is:
esoterica
'secret' is the definition.
(I know that esoterica is a type of secret)
'drunkard hides in english heather' is the wordplay.
'drunkard' becomes 'sot' (sot can mean a drunken person).
'hides in' is an insertion indicator.
'english' becomes 'E' (abbreviation).
'heather' becomes 'erica' (the plant genus Erica includes heather plants).
'e'+'erica'='eerica'
'sot' put within 'eerica' is 'ESOTERICA'.
'things' acts as a link.
(Other definitions for esoterica that I've seen before include "narrow fields" , "Coarse tie? (anag)" , "Obscure things" , "collection of specialist stuff" , "Obscure ideas" .)