This may cause amusement when manually operated (5)
I believe the answer is:
glove
'this may cause amusement when manually operated' is the definition.
Although both the answer and definition are singular nouns, I don't see how they can define each other.
'this may cause' is the wordplay.
I cannot quite understand how this works, but
'cause' could be 'love' (love is a kind of cause) and 'love' is found in the answer.
A single letter 'g' remains which might be clued in a way I don't understand.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for glove that I've seen before include "one on hand?" , "protective wear on" , "Hand-cover" , "On-hand children's entertainer?" , "hands warmer" .)