Re-reading letters from one of the guards (9)
I believe the answer is:
grenadier
'one of the guards' is the definition.
Although both the answer and definition are singular nouns, I can't understand how one could define the other.
're-reading letters' is the wordplay.
're-reading' becomes 'rereading' ('reread' can be a synonym of 're-read').
'letters' indicates anagramming the letters.
'rereading' with letters rearranged gives 'GRENADIER'.
'from' is the link.
Can you help me to learn more?
(Other definitions for grenadier that I've seen before include "guard" , "historical bomber" , "A household infantryman" , "Soldier; fish; bird" , "Soldier - in red gear (anag)" .)