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on-duty
on-duty adj. 
/ˌɒnˈdʒuːti/, /ˌɑnˈd(j)udi/ that is on duty; performed, occurring, or available while on duty.
Brit. /ˌɒnˈdjuːti/
, /ˌɒnˈdjuːti//ˌɒnˈdʒuːti/U.S. /ˌɔnˈd(j)udi/
, /ˌɔnˈd(j)udi//ˌɑnˈd(j)udi/ΘΚΠ
society > occupation and work > working > [adjective] > working
workingOE
on duty1667
on-duty1942
1942 Amer. Sociol. Rev. 7 48 It seems reasonable that the on-duty observations of trained observers..give at least a broadly correct picture.
1970 K. Platt Pushbutton Butterfly (1971) xiv. 155 The on-duty cop outside the room.
1991 Police May 19 (advt.) Whether for on-duty or off-duty carry, a Taurus pistol is the right choice.
2000 Dunoon Observer & Argyllshire Standard 1 Apr. 6/3 He had also resisted, obstructed, hindered and molested two on-duty police officers.
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