Not many seen in cafe window (3)
I believe the answer is:
few
'not many' is the definition.
('few' is the opposite to 'many')
'in cafe window' is the wordplay.
'in' indicates a hidden word.
'FEW' is hidden in the letters of 'cafe window'.
'seen' is the link.
(Other definitions for few that I've seen before include "Hardly anyone" , "'''Many are called but ... are chosen'' (Bible) (3)'" , "Not many, just a handful" , "Considerable number, ironically" , "Only one or two" .)