Royal couple to flirt? (9)
I believe the answer is:
philander
'flirt?' is the definition.
(synonyms)
'royal couple' is the wordplay.
I cannot quite see how this works, but
'royal' could be 'er' (abbreviation for Elizabeth Regina) and 'er' is present in the answer.
This explanation may well be incorrect...
'to' is the link.
Can you help me to learn more?
(Other definitions for philander that I've seen before include "Have an affair" , "Womanize" , "Have affairs" , "Flirt, chase women" , "Play around" .)