Actor about to end the affair, nominally (5)
I believe the answer is:
hiram
'affair nominally' is the definition.
I can't tell whether this defines the answer.
'actor about to end' is the wordplay.
'actor' becomes 'ham' (ham actor is a kind of actor).
'about' means one lot of letters goes inside another.
'to end' becomes 'ir' (I can't justify this - if you can you should believe this answer much more).
'ham' going around 'ir' is 'HIRAM'.
'the' is the link.
Can you help me to learn more?
(Other definitions for hiram that I've seen before include "I gave Solomon materials for Temple" , "He supplied temple builders" .)