Where, abroad, a piece of cake can take any form (5)
I believe the answer is:
kenya
'where abroad a piece' is the definition.
The answer is a location as well as being a singular noun. This is suggested by the definition.
'cake can take any form' is the wordplay.
'cake can' becomes 'ke' (I am not sure about this - if you are sure you should believe this answer much more).
'take' is a charade indicator (letters next to each other).
'form' indicates anagramming the letters.
'any' with letters rearranged gives 'nya'.
'ke'+'nya'='KENYA'
'of' is the link.
Can you help me to learn more?
(Other definitions for kenya that I've seen before include "E African country" , "Republic in East Africa" , "Land" , "East African republic" , "East African country" .)