Dry in half a mo (3)
I believe the answer is:
sec
I believe this is a double definition.
'dry' is the first definition.
(similar in meaning)
'half a mo' is the second definition.
(I've seen this in another clue)
'in' is the link.
(Other definitions for sec that I've seen before include "sparkling?" , "Dry wine perhaps" , "(Of wines) dry" , "Religious group." , "very short space of time" .)