Basic component of Windows is nonsensical for the most part (4)
I believe the answer is:
sill
'basic component of windows is' is the definition.
I can't tell whether this definition defines the answer.
'nonsensical for the most part' is the wordplay.
'nonsensical' becomes 'silly' (I've seen this in another clue).
'for the most part' means to remove the last letter.
'silly' with its final letter removed is 'SILL'.
Can you help me to learn more?
(Other definitions for sill that I've seen before include "Shelf at the foot of a window" , "Horizontal intrusion of igneous rock between sedimentaries, as in much of Hadrian's Wall" , "Horizontal timber forming the bottom of a framework" , "Ledge beneath a window" , "Window edge" .)