Upset Queen with small reminder to save (6)
I believe the answer is:
rescue
'save' is the definition.
(rescuing is a kind of saving)
'upset queen with small reminder' is the wordplay.
'upset' shows that the letters should be reversed in order.
'queen' becomes 'ER' (abbreviation for Elizabeth Regina).
'with' is a charade indicator (letters next to each other).
'small' becomes 's' (abbreviation - e.g. clothes size).
'reminder' becomes 'cue' (I've seen this in another clue).
'er' reversed gives 're'.
're'+'s'+'cue'='RESCUE'
'to' is the link.
(Other definitions for rescue that I've seen before include "Extricate" , "Retrieve" , "Salvage" , "delivery" , "Set free from harm and evil" .)