Rhea's grandmother loves to go on date (6)
I believe the answer is:
nandoo
'rhea's' is the definition.
I don't know anything about this answer so I can't judge whether this works.
'grandmother loves to go on date' is the wordplay.
I cannot quite understand how this works, but
'grandmother' could be 'nan' (nan can informally mean a grandmother) and 'nan' is found within the answer.
'loves' could be 'oo' (love means 0 in tennis) and 'oo' is found within the answer.
'date' could be 'd' (common abbreviation eg in DOB, date of birth) and 'd' is found within the answer.
No letters remain.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for nandoo that I've seen before include "Non-flying bird" , ""flightless bird"" .)