Live performances involving Australian women at top of two large power units (9)
I believe the answer is:
gigawatts
'large power units' is the definition.
(a gigawatt is a large amount of power)
'live performances involving australian women at top of two' is the wordplay.
'live performances' becomes 'gigs'.
'involving' is an insertion indicator.
'australian' becomes 'A'.
'women' becomes 'w'.
'top of' suggests taking the first letters.
The initial letter of 'two' is 't'.
'a'+'w'+'at'+'t'='awatt'
'gigs' placed around 'awatt' is 'GIGAWATTS'.
(Another definition for gigawatts that I've seen is " great power".)