Almost knocked over hot drink (4)
I believe the answer is:
nigh
'almost' is the definition.
('nigh' can be a synonym of 'almost')
'knocked over hot drink' is the wordplay.
'knocked over' says the letters should be written backwards.
'hot' becomes 'h'.
'drink' becomes 'gin' (gin is a kind of drink**).
'h'+'gin'='hgin'
'hgin' written backwards gives 'NIGH'.
(Other definitions for nigh that I've seen before include "in the vicinity?" , "Near at hand" , "Old word for near, as the end may be" , "'Almost, near (4)'" , "old touch" .)