He's a father to many soldiers (5)
I believe the answer is:
padre
'he's a' is the definition.
The answer is a person as well as being a singular noun. This is suggested by the definition.
'father to many soldiers' is the wordplay.
'father' becomes 'pa' (pa can mean dad or father).
'to many' becomes 'D' (Roman numeral for 500).
'soldiers' becomes 're' (Royal Engineers).
'pa'+'d'+'re'='PADRE'
Can you help me to learn more?
(Other definitions for padre that I've seen before include "Man of god - drape (anag)" , "Services' chaplain" , "Father" , "Military chaplain" , "A military clergyman" .)