Measure taken by the police again (5)
I believe the answer is:
metre
'measure' is the definition.
(I know that measure can be written as metre)
'by the police again' is the wordplay.
'by' means one lot of letters go next to another.
'the police' becomes 'met' (London Metropolitan Police).
'again' becomes 're' (prefix meaning 'again').
'met'+'re' is 'METRE'.
'taken' is the link.
(Other definitions for metre that I've seen before include "Moisture remover" , "three and a bit of a fourth" , "Poetic rhythm" , "Approx 39 inches" , "measure of length" .)