Blotter used to hold one set of words (8)
I believe the answer is:
libretto
'set of words' is the definition.
'libretto' can be an answer for 'words' (I've seen this before). I am unsure of the 'set of' bit.
'blotter used to hold one' is the wordplay.
'used' indicates anagramming the letters.
'to hold' is an insertion indicator.
'one' becomes 'i' (Roman numeral).
'blotter' is an anagram of 'lbretto'.
'lbretto' placed around 'i' is 'LIBRETTO'.
Can you help me to learn more?
(Other definitions for libretto that I've seen before include "Operatic book" , "text for musicians" , "textbook" , "Words set to music, especially opera" , "Operatic text" .)