Something disappointing leading journalist's written up in daily (2,5)
I believe the answer is:
le monde
'daily' is the definition.
(Le Monde is a French daily newspaper)
'something disappointing leading journalist's written up' is the wordplay.
'something disappointing' becomes 'lemon' (lemon can mean a faulty or unsatisfactory thing).
'leading journalist' becomes 'ed' (short for editor).
'written up' shows that the letters should be reversed in order.
'ed' in reverse letter order is 'de'.
'lemon'+'de'='LE MONDE'
'in' is the link.
(Other definitions for le monde that I've seen before include "paper" , "French newspaper" , "Where journalists are employed" , "European newspaper" .)