Local Iron Age development on lake (8)
I believe the answer is:
regional
'local' is the definition.
(in a particular region)
'iron age development on lake' is the wordplay.
'development' is an anagram indicator.
'on' is a charade indicator (letters next to each other).
'lake' becomes 'l' (geographical abbreviation).
'iron'+'age'='ironage'
'ironage' is an anagram of 'regiona'.
'regiona'+'l'='REGIONAL'
(Other definitions for regional that I've seen before include "Relating to local area" , "Relating to a particular area" , "Limited to a particular part of the country - liar gone (anag)" , "Territorial" , "Characteristic of an area" .)