Publicity seen by thirsty nymphs (6)
I believe the answer is:
dryads
'nymphs' is the definition.
(dryads are tree nymphs in Greek myth)
'publicity seen by thirsty' is the wordplay.
'publicity' becomes 'ads' (advert).
'seen by' says to put letters next to each other.
'thirsty' becomes 'dry' (similar in meaning).
'ads' put after 'dry' is 'DRYADS'.
(Other definitions for dryads that I've seen before include "Nymphs of the woods" , "Tree-nymphs." , "spirits" , "Wood nymphs of legend" , "Tree nymphs" .)