True manuscript from the fields of activity (6)
I believe the answer is:
realms
'fields of activity' is the definition.
'realms' can be an answer for 'fields' ('realm' can be a synonym of 'field'). I am not certain of the 'of activity' bit.
'true manuscript from' is the wordplay.
I cannot quite see how this works, but
'true' could be 'real' (synonyms) and 'real' is found in the answer.
'manuscript' could be 'ms' (abbreviation for manuscript) and 'ms' is found within the answer.
No letters remain.
This may be the basis of the clue (or it may be nonsense).
'the' is the link.
Can you help me to learn more?
(Other definitions for realms that I've seen before include "Fields of activity or interest - sound monarchical" , "regions" , "Domains ruled by king or queen" , "Kingdoms, or fields of interest" , "Domains - provinces" .)