He explored old towns initially by hired car (5)
I believe the answer is:
cabot
'he explored' is the definition.
(Italian navigator John Cabot)
'old towns initially by hired car' is the wordplay.
'initially' suggests taking the first letters.
'by' says to put letters next to each other.
'hired car' becomes 'cab' (I've seen this before).
The first letters of 'old towns' is 'ot'.
'ot' after 'cab' is 'CABOT'.
(Other definitions for cabot that I've seen before include "John (Giovanni) -, navigator, explored N. America" , "famous explorer" , "Sebastian & John -, early navigators" , "Italian explorer (father or son)" , "One of two explorers" .)