Large plant around a cold lake produces molasses (7)
I believe the answer is:
treacle
'molasses' is the definition.
(thesaurus)
'large plant around a cold lake' is the wordplay.
'large plant' becomes 'tree' (I've seen this before).
'around' indicates putting letters inside.
'a cold' becomes 'ac' (I've seen this in other clues).
'lake' becomes 'l'.
'ac'+'l'='acl'
'tree' going around 'acl' is 'TREACLE'.
'produces' acts as a link.
(Other definitions for treacle that I've seen before include "Golden syrup" , "refined product" , "Sticky produce" , "Thick syrup from sugar cane" , "Sweet, black viscous substance" .)