Lesser volume partly filling spot? (5)
I believe the answer is:
servo
'filling spot?' is the definition.
The definition and answer can be both man-made objects as well as being singular nouns.
Perhaps there's a link between them I don't understand?
'lesser volume partly' is the wordplay.
'partly' says the answer is hidden in the clue (part of the clue is used).
'SERVO' can be found hidden inside 'lesser volume'.
Can you help me to learn more?
(Other definitions for servo that I've seen before include "Mechanism augmenting force or motion" , "car mechanism" , "Assisting motor" , "Control system" , "Powered control mechanism" .)