How Joe functions in a doodah (5)
I believe the answer is:
gismo
'functions in a doodah' is the definition.
I don't know anything about this answer so I cannot judge whether this works.
'how joe' is the wordplay.
I cannot quite understand how this works, but
'joe' could be 'gi' (GI Joe) and 'gi' is found within the answer.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for gismo that I've seen before include "Gadget (colloq.)" , "mechanical device?" , "Fancy device" , "Device of American" , "Useful gadget" .)