Sign of maturity suppressed by most of journalists (7)
I believe the answer is:
presage
'sign' is the definition.
(I know that presage is a type of sign)
'maturity suppressed by most of journalists' is the wordplay.
'maturity' becomes 'age' (I've seen this before).
'suppressed by' means one lot of letters go next to another.
'most of' means to remove the last letter.
'journalists' becomes 'press' (the press can mean the newspaper industry).
'press' with its last letter taken away is 'pres'.
'age' put after 'pres' is 'PRESAGE'.
'of' is the link.
(Other definitions for presage that I've seen before include "Be an advance sign of, portend" , "Portent" , "Forecast, foreshadow" , "Foretell" , "Be a sign of (something)" .)