Right around lunchtime, love to have a threesome (4)
I believe the answer is:
trio
'a threesome' is the definition.
(both can mean a group of three)
'right around lunchtime love' is the wordplay.
'right' becomes 'rt' (abbreviation as in Rt Hon- the Right Honourable).
'around' says the letters should be written in reverse.
'lunchtime' becomes 'I' (1pm could be I on a clock with Roman numerals).
'love' becomes 'o' (love means zero in tennis).
'rt' in reverse letter order is 'tr'.
'tr'+'i'+'o'='TRIO'
'to have' is the link.
(Other definitions for trio that I've seen before include "Beethoven's 'Archduke', for example" , "Ensemble musical piece, eg Beethoven's 'Archduke'" , "Group of Magi?" , "Band of three" , "Musical group" .)