Dry in half a moment (3)
I believe the answer is:
sec
'dry' is the definition.
('sec' can be similar in meaning to 'dry')
'half a moment' is the wordplay.
'half a' suggests halving the letters.
'moment' becomes 'second' (second moment is a kind of moment).
'second' cut in half is 'SEC'.
'in' is the link.
(Other definitions for sec that I've seen before include "21 down, as wine" , "Mo or min?" , "Dry wine perhaps" , "Moderately dry, champagne say" , "Twinkling" .)