Relative emptied out Austin that's dirty (7)
I believe the answer is:
unclean
'dirty' is the definition.
(I know that dirty can be written as unclean)
'relative emptied out austin' is the wordplay.
'relative' becomes 'uncle' (uncle is a kind of relative).
'emptied out' means to remove the middle letters (the inside letters are emptied out).
'austin' with its middle taken out is 'an'.
'uncle'+'an'='UNCLEAN'
'that's' is the link.
(Other definitions for unclean that I've seen before include "taboo" , "(Ritually) tainted" , "Spotted" , "Dirty, needs a wash" , "Dirty; immoral" .)