Detectives starting to bend and break up (7)
I believe the answer is:
disband
'break up' is the definition.
(disbanding is a kind of breaking up)
'detectives starting to bend and' is the wordplay.
'detectives' becomes 'dis' (Detective Inspectors, DIs).
'starting to' says to take the initial letters.
The initial letter of 'bend' is 'b'.
'dis'+'b'+'and'='DISBAND'
(Other definitions for disband that I've seen before include "shed" , "Scatter" , "Dissolve" , "Break up as a group" , "Cease to be a group" .)