Nymphs being dull and awfully sad (6)
I believe the answer is:
dryads
'nymphs' is the definition.
(dryads are tree nymphs in Greek myth)
'dull and awfully sad' is the wordplay.
'dull' becomes 'dry' (I've seen this before).
'and' is a charade indicator (letters next to each other).
'awfully' is an anagram indicator.
'sad' is an anagram of 'ads'.
'dry'+'ads'='DRYADS'
'being' acts as a link.
(Other definitions for dryads that I've seen before include "Nymphs of the woods" , "Tree nymphs" , "spirits" , "Tree-nymphs." , "Wood nymphs of legend" .)