Have concern about daughter in military unit (5)
I believe the answer is:
cadre
'military unit' is the definition.
(I've seen this before)
'have concern about daughter' is the wordplay.
'have concern' becomes 'care' (I've seen this in another clue).
'about' means one lot of letters goes inside another.
'daughter' becomes 'd' (genealogical abbreviation).
'care' enclosing 'd' is 'CADRE'.
'in' acts as a link.
(Other definitions for cadre that I've seen before include "Raced (anag) -- small inner group of activists" , "team" , "Nucleus of servicemen" , "Inner group of activists in a revolutionary party" , "Nucleus, framework" .)