Police department brings in lots -- all about to become vigorous (7)
I believe the answer is:
dynamic
'vigorous' is the definition.
('dynamic' can be similar in meaning to 'vigorous')
'police department brings in lots all about' is the wordplay.
'police department' becomes 'cid' (I've seen this in other clues).
'brings in' means one lot of letters goes inside another.
'lots' becomes 'many' (I've seen this before).
'all about' says the letters should be written in reverse.
'cid' placed around 'many' is 'cimanyd'.
'cimanyd' in reverse letter order is 'DYNAMIC'.
'to become' is the link.
(Other definitions for dynamic that I've seen before include "Energetic, with great force of character" , "Constantly changing" , "High-powered" , "Vigorous and effective" , "Having power" .)