An elite unit lacking one injured soldier (10)
I believe the answer is:
lieutenant
'soldier' is the definition.
The definition and answer can be both people as well as being singular nouns.
Maybe there's an association between them I don't understand?
'an elite unit lacking one injured' is the wordplay.
'lacking' is a deletion indicator.
'one' becomes 'i' (Roman numeral).
'injured' indicates an anagram.
'an'+'elite'+'unit'='aneliteunit'
'aneliteunit' with 'i' removed is 'anelteunit'.
'anelteunit' with letters rearranged gives 'LIEUTENANT'.
Can you help me to learn more?
(Other definitions for lieutenant that I've seen before include "Substitute" , "Army officer" , "Deputy" , "Army rank" , "Assistant" .)