National language used by staff (10)
I believe the answer is:
englishman
'national' is the definition.
The definition and answer can be both people as well as being singular nouns.
Perhaps they are linked in a way I don't understand?
'language used by staff' is the wordplay.
'language' becomes 'english' (English language is an example).
'used by' says to put letters next to each other.
'staff' becomes 'man' (as in staffing or manning a particular place).
'english'+'man'='ENGLISHMAN'
Can you help me to learn more?
(Other definitions for englishman that I've seen before include "European" , "Native" , "Bennett's abroad (Burgess)" , "E.g. Coward's idiot at 12" , "For example, Ralph Rackstraw" .)