Australian unusually cites creed's opening, being of austere outlook (7)
I believe the answer is:
ascetic
'being of austere outlook' is the definition.
(ascetic means austere or strict)
'australian unusually cites creed's opening' is the wordplay.
'australian' becomes 'a' (common abbreviation).
'unusually' indicates an anagram.
'opening' says to take the initial letters.
The initial letter of 'creeds' is 'c'.
'cites'+'c'='citesc'
'citesc' anagrammed gives 'scetic'.
'a'+'scetic'='ASCETIC'
(Other definitions for ascetic that I've seen before include "Austere disciple" , "One who practises severe selfdenial" , "Severely self-disciplined" , "Self-denier" , "Austere, abstinent" .)