French boyfriend engaged in surreptitious relations (6)
I believe the answer is:
family
'relations' is the definition.
(thesaurus)
'french boyfriend engaged in surreptitious' is the wordplay.
'french boyfriend' becomes 'ami' (a male friend in French. I am not sure about the 'french' bit.).
'engaged in' means one lot of letters goes inside another.
'surreptitious' becomes 'fly' (fly can mean crafty or surreptitious).
'ami' put within 'fly' is 'FAMILY'.
Can you help me to learn more?
(Other definitions for family that I've seen before include "Close-knit group" , "Means-tested benefit for working people with children, paid from 1971 to 1986" , "Group of related things" , "Group of people related to one another" , "Closely related group" .)