Loud fellow in South African river with slight cold (7)
I believe the answer is:
sniffle
'slight cold' is the definition.
(I've seen this before)
'loud fellow in south african river' is the wordplay.
'loud' becomes 'f' (short for forte - 'loud' in music).
'fellow' becomes 'f' (abbreviation - of a society etc.).
'in' indicates putting letters inside.
'south' becomes 'S' (abbreviation).
'african river' becomes 'nile' (I've seen this before).
'f'+'f'='ff'
's'+'nile'='snile'
'ff' inserted within 'snile' is 'SNIFFLE'.
'with' acts as a link.
(Other definitions for sniffle that I've seen before include "Sign of a cold?" , "Breathe in, as when having a cold" , "A little cold" , "Slight head cold" , "Mild cold" .)