Pacino about to blitz last Australian regimental leader in Spanish fortress (7)
I believe the answer is:
alcazar
'spanish fortress' is the definition.
(I've seen this in another clue)
'pacino about to blitz last australian regimental leader' is the wordplay.
'pacino' becomes 'al' (Al Pacino).
'about' becomes 'ca' (abbreviation for 'circa').
'to' says to put letters next to each other.
'last' says to take the final letters.
'leader' suggests taking the first letters.
The final letter of 'blitz' is 'z'.
The first letters of 'australian regimental' is 'ar'.
'al'+'ca'+'z'+'ar'='ALCAZAR'
'in' acts as a link.
(Other definitions for alcazar that I've seen before include "Moorish palace in Spain" , "Spanish palace" .)