Instinct about welcoming policeman, a patent expert? (6)
I believe the answer is:
edison
'a patent expert?' is the definition.
(inventor Thomas Edison)
'instinct about welcoming policeman' is the wordplay.
'instinct' becomes 'nose' (a nose for something is a good instinct for it).
'about' says the letters should be written backwards.
'welcoming' indicates putting letters inside (in sense of 'inviting in').
'policeman' becomes 'di' (I've seen this in other clues).
'nose' reversed gives 'eson'.
'eson' placed around 'di' is 'EDISON'.
(Other definitions for edison that I've seen before include "US scientist/inventor" , "Inventor of the light bulb" , "Science master" , "Inventor of the carbon filament lamp, d. 1931" , "Prolific inventor" .)