After short time, like fiddle that's taken up theme (5)
I believe the answer is:
motif
'theme' is the definition.
(I know that motif is a type of theme)
'after short time like fiddle that's taken up' is the wordplay.
'after' says to put letters next to each other.
'short time' becomes 'mo' (as in 'just a mo').
'like fiddle' becomes 'fit' (I can't explain this - if you can you should believe this answer much more).
'that's taken up' says the letters should be written backwards.
'fit' written backwards gives 'tif'.
'mo'+'tif' is 'MOTIF'.
Can you help me to learn more?
(Other definitions for motif that I've seen before include "Recurring image in design" , "recurring idea" , "Characteristic theme" , "Logo -- pattern" , "Unifying idea in an artistic work" .)