Cut the number in custody (5)
I believe the answer is:
carve
'cut' is the definition.
(carving is a kind of cutting)
'number in custody' is the wordplay.
'number' becomes 'v' (V is an example).
'in' is an insertion indicator.
'custody' becomes 'care' (I've seen this in another clue).
'v' going within 'care' is 'CARVE'.
'the' is the link.
(Other definitions for carve that I've seen before include "Attack the turkey" , "Truncheon" , "fashion" , "Chisel, sculpt" , "Cut into pieces" .)