A joy almost certainly found in journalist that's discerning (5-4)
I believe the answer is:
eagle-eyed
'discerning' is the definition.
'a joy almost certainly found in journalist' is the subsidiary indication.
'joy' becomes 'glee' (I've seen this before**).
'almost' means to remove the last letter.
'certainly' becomes 'yes' (I've seen this before).
'found in' indicates putting letters inside.
'journalist' becomes 'ed'.
'yes' with its final letter removed is 'ye'.
'a'+'glee'+'ye'='agleeye'
'agleeye' placed inside 'ed' is 'eagleeyed'.
'that's' is the link.
(Other definitions for eagle-eyed that I've seen before include "Watching closely" , "Keenly observant" , "Sharp of vision like noble bird" , "(Of someone) keeping a close watch" , "Keen-sighted" .)