The pointlessness of putting a flat roof on a work vehicle (8)
I believe the answer is:
futility
'the pointlessness' is the definition.
(I've seen this before)
'putting a flat roof on a work vehicle' is the wordplay.
I cannot quite understand how this works, but
'work' could be 'utility' (utility is a kind of work) and 'utility' is found in the answer.
A single letter 'f' remains which might be clued in a way I don't see.
This may be the basis of the clue (or it may be nonsense).
'of' is the link.
Can you help me to learn more?
(Other definitions for futility that I've seen before include "No prospect of success" , "Uselessness" , "Pointlessness" .)