Frantic fear and trepidation initially concerning (5)
I believe the answer is:
after
'frantic fear and trepidation initially concerning' is the definition.
I can't judge whether this defines the answer.
'frantic fear and trepidation initially' is the wordplay.
'frantic' is an anagram indicator (I've seen this in other clues).
'and' means one lot of letters go next to another.
'initially' suggests taking the first letters.
The first letter of 'trepidation' is 't'.
'fear' put after 't' is 'tfear'.
'tfear' with letters rearranged gives 'AFTER'.
Can you help me to learn more?
(Other definitions for after that I've seen before include "back along > deck" , "Coming later in time" , "Looking for" , "Following, consequent to" , "In pursuit of, behind" .)