Diary shows zero sign of organisation (4)
I believe the answer is:
logo
'sign of organisation' is the definition.
'logo' can be an answer for 'sign' (logo is a kind of sign). I am not sure about the 'of organisation' bit.
'diary shows zero' is the wordplay.
I cannot quite understand how this works, but
'diary' could be 'log' (log can mean a record or diary) and 'log' is found in the answer.
'zero' could be 'o' (O resembles 0) and 'o' is located in the answer.
This accounts for all the letters.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for logo that I've seen before include "organisational symbol" , "Corporate emblem" , "Emblem, trade-mark" , "A company's printed symbol or emblem" , "A firm's sign or symbol" .)