Seize pass, lake and river to begin with (6)
I believe the answer is:
collar
'seize' is the definition.
(collaring is a kind of seizing)
'pass lake and river to begin with' is the wordplay.
'pass' becomes 'col' (col is a term for a mountain pass).
'to begin with' indicates taking the first letters.
The first letters of 'lake and river' is 'lar'.
'col'+'lar'='COLLAR'
(Other definitions for collar that I've seen before include "Grab one" , "Band around garment's neck" , "Neckband of shirt" , "Apprehend (colloq.); cut of bacon" , "Item worn around the neck" .)