I fool around making a book (5)
I believe the answer is:
folio
'a book' is the definition.
(I've seen this before)
'i fool around' is the wordplay.
'around' indicates an anagram.
'i'+'fool'='ifool'
'ifool' with letters rearranged gives 'FOLIO'.
'making' acts as a link.
(Other definitions for folio that I've seen before include "Sheet of paper folded to make two book leaves" , "Body of written work" , "eaf" , "Leaf of paper" , "File" .)