Initially glimpsed weaving machine in partial darkness (5)
I believe the answer is:
gloom
'partial darkness' is the definition.
(I've seen this before)
'initially glimpsed weaving machine' is the wordplay.
'initially' says to take the initial letters.
'weaving machine' becomes 'loom' (I've seen this before).
The first letter of 'glimpsed' is 'g'.
'g'+'loom'='GLOOM'
'in' acts as a link.
(Other definitions for gloom that I've seen before include "Obscurity or melancholy" , "Darkness; depression" , "Betting figures" , "Murkiness" , "Despondency" .)