At last, dessert, in a city in Australia - it's a beer (5)
I believe the answer is:
tinny
'australia it's a beer' is the definition.
I can't judge whether this defines the answer.
'at last dessert in a city' is the wordplay.
'at last' indicates one should take the final letters.
'a city' becomes 'ny' (short for New York).
The last letter of 'dessert' is 't'.
't'+'in'+'ny'='TINNY'
'in' is the link.
Can you help me to learn more?
(Other definitions for tinny that I've seen before include "Of poor audio quality" , "Lacking resonance" , "insubstantial" , "Sounding thin and metallic" , "appear so badly constructed?" .)