Assemble kit in a good mood (3,2)
I believe the answer is:
rig up
'assemble' is the definition.
(I know that rig up is a kind of assemble)
'kit in a good mood' is the wordplay.
I cannot quite understand how this works, but
'kit' could be 'rig' (I've seen this before) and 'rig' is found within the answer.
The remaining letters 'up' is a valid word which might be clued in a way I don't understand.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for rig up that I've seen before include "Make temporary arrangement" , "Construct in a makeshift way" , "Put (structure) together" , "Cobble together" , "fix" .)