Identical small females throwing tantrum (8)
I believe the answer is:
selfsame
'identical' is the definition.
('selfsame' can be a synonym of 'identical')
'small females throwing tantrum' is the wordplay.
'small' becomes 's' (abbreviation - e.g. clothes size).
'throwing tantrum' indicates an anagram.
'females' is an anagram of 'elfsame'.
's'+'elfsame'='SELFSAME'
(Other definitions for selfsame that I've seen before include "The identical kind, not changed or different" , "Exactly identical" .)