Merman or Mertz (5)
I believe the answer is:
ethel
'merman or mertz' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for ethel that I've seen before include "Lady" , "Perhaps a Barrymore" , "woman" , "- Barrymore, actress" , "Lethe (anag) -- Barrymore or Merman" .)