Small book, one carried by match official (5)
I believe the answer is:
brief
'small' is the definition.
'book one carried by match official' is the wordplay.
'book' becomes 'b'.
'one' becomes 'i' (Roman numeral).
'carried by' means one lot of letters goes inside another.
'match official' becomes 'ref' (I've seen this in other clues).
'i' put within 'ref' is 'rief'.
'b'+'rief'='BRIEF'
(Other definitions for brief that I've seen before include "Barrister (sl.)" , "Brusque - lawyer (slang)" , "Short in duration" , "Short - work for counsel" , "Fibre (anag.)" .)