Watched a little yacht in river capsizing (4)
I believe the answer is:
eyed
'watched' is the definition.
(I've seen this before)
'a little yacht in river capsizing' is the wordplay.
'a little' suggests taking the first letters.
'in' indicates putting letters inside.
'river' becomes 'dee' (River Dee).
'capsizing' shows that the letters should be reversed in order.
The initial letter of 'yacht' is 'y'.
'y' going into 'dee' is 'deye'.
'deye' in reverse letter order is 'EYED'.
(Other definitions for eyed that I've seen before include "examined" , "Saw" , "Watched with interest" , "Ogled" , "Stared at" .)