One negative effect that's associated with station (5)
I believe the answer is:
ident
'station' is the definition.
Both the definition and answer are singular nouns.
Maybe you can see an association between them that I don't see?
'one negative effect that's associated with' is the wordplay.
'one' becomes 'i' (Roman numeral).
'negative effect' becomes 'dent' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'that's associated with' says to put letters next to each other.
'i'+'dent'='IDENT'
Can you help me to learn more?
(Other definitions for ident that I've seen before include "not much, which shows your station" , "image on screen" , "short film sequence" , "Broadcast indicating TV channel" , "Short BBC sequence" .)