One direction or another is not so good (5)
I believe the answer is:
worse
'not so good' is the definition.
(I've seen this in another clue)
'one direction or another' is the wordplay.
'one direction' becomes 'W' (W is an example).
'another' becomes 'se' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'w'+'or'+'se'='WORSE'
'is' is the link.
Can you help me to learn more?
(Other definitions for worse that I've seen before include "More serious" , "Of poorer quality" , "more unpleasant" , "Less good" , "Inferior to another" .)