The best thing that goes with strawberries (5)
I believe the answer is:
cream
I believe this clue is a double definition.
'the best' is the first definition.
(as in 'the cream of the crop')
'thing that goes with strawberries' is the second definition.
(as in strawberries and cream)
(Other definitions for cream that I've seen before include "An off-white shade" , "The best part -of the crop" , "Top or best part" , "Elite; off-white" , "Top of milk or society" .)