Take a seat anew, at length (5)
I believe the answer is:
steal
'take' is the definition.
(I know that steal is a more specific form of the action take)
'a seat anew at length' is the wordplay.
'anew' is an anagram indicator.
'at' says to put letters next to each other.
'length' becomes 'l' (abbreviation in geometry).
'seat' anagrammed gives 'stea'.
'stea'+'l'='STEAL'
(Other definitions for steal that I've seen before include "Snatch" , "Nick" , "Rob" , "crib" , "Filch" .)