Tree-dweller featuring in sundry advertisements (5)
I believe the answer is:
dryad
'tree-dweller' is the definition.
(type of spirit in Greek myth)
'in sundry advertisements' is the wordplay.
'in' indicates the answer is hidden within the clue.
'DRYAD' is hidden in the letters of 'sundry advertisements'.
'featuring' acts as a link.
(Other definitions for dryad that I've seen before include "Nymph of trees" , "Woodland nymph" , "Beautiful young woman" , "minor divinity" , "Nymph of the woods" .)