Bet and Sara may be side by side (7)
I believe the answer is:
abreast
'side by side' is the definition.
(synonyms)
'bet and sara may be' is the wordplay.
'and' is a charade indicator (letters next to each other).
'may be' indicates an anagram.
'bet' put after 'sara' is 'sarabet'.
'sarabet' anagrammed gives 'ABREAST'.
(Other definitions for abreast that I've seen before include "to be up to date" , "Side by side - in the picture" , "Well-informed" , "Level in line" , "shoulder to shoulder" .)