Initially concerned with terribly rare helper (5)
I believe the answer is:
carer
'helper' is the definition.
Both the definition and answer are singular nouns.
Maybe they are linked in a way I don't understand?
'initially concerned with terribly rare' is the wordplay.
'initially' suggests taking the first letters.
'with' is a charade indicator (letters next to each other).
'terribly' indicates anagramming the letters.
The first letter of 'concerned' is 'c'.
'rare' is an anagram of 'arer'.
'c'+'arer'='CARER'
Can you help me to learn more?
(Other definitions for carer that I've seen before include "Nurse, perhaps," , "Attendant in nursing home" , "Welfare worker" , "one into social welfare?" , "One who looks after sick or disabled person at home" .)