A lieutenant meeting the queen has to change (5)
I believe the answer is:
alter
'change' is the definition.
(synonyms)
'a lieutenant meeting the queen' is the wordplay.
'lieutenant' becomes 'lt' (abbreviation for lieutenant).
'meeting' is a charade indicator (letters next to each other).
'the queen' becomes 'ER' (Elizabeth Regina).
'a'+'lt'+'er'='ALTER'
'has to' acts as a link.
(Other definitions for alter that I've seen before include "Revise" , "reform" , "Metamorphose" , "Alert to change" , "Vary" .)