Just missing out on bronze and uranium in river (6)
I believe the answer is:
fourth
'just missing out on bronze' is the definition.
Both the definition and answer are adjectives. Maybe you can see an association between them that I can't see?
'uranium in river' is the wordplay.
'uranium' becomes 'U' (U is the chemical symbol for uranium).
'in' means one lot of letters goes inside another.
'river' becomes 'Forth' (Scottish river).
'u' going into 'forth' is 'FOURTH'.
'and' is the link.
Can you help me to learn more?
(Other definitions for fourth that I've seen before include "not among the medal winners?" , "Ordinal number for the press - the . . . . . . estate" , "Placed just after the winners" , "C-F musical interval -- Prince Regent George's eventual regnal number" , "Behind the top three" .)