Less faultless service outside the shopping precinct (7)
I believe the answer is:
smaller
'less' is the definition.
(thesaurus)
'faultless service outside the shopping precinct' is the wordplay.
'faultless service' becomes 'ser' (I can't explain this - if you can you should give a lot more credence to this answer).
'outside' means one lot of letters goes inside another.
'the shopping precinct' becomes 'mall' (I've seen this before).
'ser' placed around 'mall' is 'SMALLER'.
Can you help me to learn more?
(Other definitions for smaller that I've seen before include "Not as big as" , "Less extensive" , "More diminutive" , "Sell ram (anag.)" .)