Turn from a lieutenant meeting queen (5)
I believe the answer is:
alter
'turn' is the definition.
(I know this)
'a lieutenant meeting queen' is the wordplay.
'lieutenant' becomes 'lt' (abbreviation for lieutenant).
'meeting' means one lot of letters go next to another.
'queen' becomes 'ER' (abbreviation for Elizabeth Regina).
'a'+'lt'+'er'='ALTER'
'from' acts as a link.
(Other definitions for alter that I've seen before include "and 10 Across: Second self" , "Vary" , "Make changes to" , "Amend" , "Change or adjust" .)