Organised tour takes in republic's first city (5)
I believe the answer is:
truro
'city' is the definition.
(I have seen 'Cornish city' mean 'truro' so perhaps 'city' could also mean 'truro')
'organised tour takes in republic's first' is the wordplay.
'organised' indicates an anagram.
'takes in' means one lot of letters goes inside another.
'republic's first' becomes 'r' (1st letter of 'republic').
'tour' anagrammed gives 'truo'.
'truo' placed around 'r' is 'TRURO'.
(Other definitions for truro that I've seen before include "The Island of Doctor - (H. G. Wells)" , "Cornish county town" , "One slain by Cain" , "Cornish market town" , "City of Cornwall" .)