Current contained by broken cattle grid (7)
I believe the answer is:
lattice
'grid' is the definition.
(I've seen this before)
'current contained by broken cattle' is the wordplay.
'current' becomes 'I' (symbol for electric current).
'contained by' means one lot of letters goes inside another.
'broken' indicates anagramming the letters.
'cattle' is an anagram of 'lattce'.
'i' going within 'lattce' is 'LATTICE'.
(Other definitions for lattice that I've seen before include "Sort of window" , "Openwork structure" , "Network of Wooden strips" , "Crystalline structure" , "grill" .)