Singer Moyet left first to hide one love affair (7)
I believe the answer is:
liaison
'love affair' is the definition.
(I've seen this in another clue)
'singer moyet left first to hide one' is the wordplay.
I cannot quite understand how this works, but
'left' could be 'l' (common abbreviation) and 'l' is present in the answer.
'first' could be 'i' (I in Roman numerals eg Elizabeth I) and 'i' is found in the answer.
'one' could be 'i' (Roman numeral) and 'i' is present in the answer.
This explanation may well be incorrect...
(Other definitions for liaison that I've seen before include "Bond of union" , "carryon" , "Communication; relationship" , "sexual adventure" , "Secret love-affair" .)