Headwear initially tested in the city (6)
I believe the answer is:
turban
'headwear' is the definition.
(covering worn on the head)
'initially tested in the city' is the wordplay.
'initially' says to take the initial letters.
'in the city' becomes 'urban' (urban means relating to a city).
The initial letter of 'tested' is 't'.
't'+'urban'='TURBAN'
(Other definitions for turban that I've seen before include "Eastern head-dress" , "Nut bar (anag.)" , "Cloth worn as headdress by Sikh" , "Cloth wound around the head" , "Head-dress of male Muslim and Sikh" .)