In old city taking time off is fellow traveller (6)
I believe the answer is:
romany
'traveller' is the definition.
(Romany is an example)
'in old city taking time off is fellow' is the wordplay.
I cannot really understand how this works, but
'old' could be 'o' (common abbreviation eg in OE for Old English) and 'o' is found within the answer.
'city' could be 'ny' (short for New York) and 'ny' is found in the answer.
This explanation may well be incorrect...
(Other definitions for romany that I've seen before include "Traveller" , "Language of gypsies" , "Roy, man, you're a gypsy" , "Gypsy language" , "one of those travelling" .)