Goods in river an annoyance (6)
I believe the answer is:
niggle
'an annoyance' is the definition.
(I have seen 'Petty annoyance' mean 'niggle' so perhaps 'annoyance' could also mean 'niggle')
'goods in river' is the wordplay.
'goods' becomes 'gg' (I've seen this in other clues).
'in' means one lot of letters goes inside another.
'river' becomes 'nile' (Nile is an example).
'gg' going into 'nile' is 'NIGGLE'.
(Other definitions for niggle that I've seen before include "Carp" , "'Small, gnawing worry (6)'" , "Persistently irritate" , "Persistently criticise over trifles" , "Cause slight annoyance" .)