Gets rid of us to move the son in (5)
I believe the answer is:
ousts
'gets rid of' is the definition.
(I've seen this in another clue)
'us to move the son in' is the wordplay.
'move' indicates an anagram.
'the son' becomes 's' (genealogical abbreviation for son).
'in' indicates putting letters inside.
'to' is an anagram of 'ot'.
'ot'+'s'='ots'
'us' placed into 'ots' is 'OUSTS'.
(Other definitions for ousts that I've seen before include "Unseats, puts out of office" , "Removes from office" , "Forces someone out and takes their place" , "Forces out of position" , "Replaces" .)