The ADC cannot possibly be a gentleman! (3)
I believe the answer is:
cad
'a gentleman' 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?
'the adc cannot possibly' is the wordplay.
'adc' anagrams to 'CAD'.
But, I'm unsure how the anagram is indicated.
'be' is the link.
Can you help me to learn more?
(Other definitions for cad that I've seen before include "A knave, real rotter" , "That ain't no gentleman" , "Blackguard" , "he's no gent" , "Heel" .)