Large female cat (7)
(Other definitions for lioness that I've seen before include "Large cat" , "Female pride member" , "She may have pride" , "Predator" , "Fierce female feline" .)
'large female cat' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for tigress that I've seen before include "dangerous animal" , "hunting animal" , "Female wildcat" , "Large female cat" , "Ferocious female" .)