Novelty we set up in northern loch (7)
I believe the answer is:
newness
'novelty' is the definition.
(thesaurus)
'we set up in northern loch' is the wordplay.
'set up' shows that the letters should be reversed in order.
'in' means one lot of letters goes inside another.
'northern' becomes 'n' (abbreviation e.g. N. Ireland).
'loch' becomes 'ness' (I've seen this before).
'we' back-to-front is 'ew'.
'n'+'ness'='nness'
'ew' going into 'nness' is 'NEWNESS'.
(Other definitions for newness that I've seen before include "originality" , "Novelty" , "Fresh quality" , "Freshness" .)