MS unit ramps up screening considerably at first (10)
I believe the answer is:
manuscript
'ms' is the definition.
(synonyms)
'unit ramps up screening considerably at first' is the wordplay.
'up' indicates an anagram (letters get chucked up).
'screening' is an insertion indicator (inserted letters are covered or screened by others).
'at first' says to take the initial letters.
The first letter of 'considerably' is 'c'.
'unit'+'ramps'='unitramps'
'unitramps' with letters rearranged gives 'manusript'.
'manusript' placed around 'c' is 'MANUSCRIPT'.
(Other definitions for manuscript that I've seen before include "What's written" , "Original or copy of document" , "text awaiting publication" , "Handwritten text" , "Handwritten document" .)