Took account of what a cub journalist certainly is! (5)
I believe the answer is:
noted
'took account of' is the definition.
(I've seen this before)
'a cub journalist certainly is' is the wordplay.
I cannot really see how this works, but
'journalist' could be 'ed' (short for editor) and 'ed' is found within the answer.
The remaining letters 'not' is a valid word which might be clued in a way I don't see.
This explanation may well be incorrect...
'what' acts as a link.
Can you help me to learn more?
(Other definitions for noted that I've seen before include "Observed or took account of" , "written down" , "Widely known and esteemed" , "Toned down and recorded" , "Scores like this" .)