Always move different sappers to protect the Queen (8)
I believe the answer is:
evermore
'always' is the definition.
(I've seen this before)
'move different sappers to protect the queen' is the wordplay.
'different' is an anagram indicator.
'sappers' becomes 'RE' (nickname for the Royal Engineers).
'to protect' means one lot of letters goes inside another.
'the queen' becomes 'ER' (Elizabeth Regina).
'move' with letters rearranged gives '[move]'.
'[move]'+'re'='evmore'
'evmore' going around 'er' is 'EVERMORE'.
(Other definitions for evermore that I've seen before include "Forever (literary)" , "For which, permanently" , "Always and without end" , "Always, forever" , "To all eternity" .)