Flood bound to brim over top of gorge (5)
I believe the answer is:
surge
'flood bound' is the definition.
'surge' can be an answer for 'flood' (thesaurus). I am unsure of the 'bound' bit.
'brim over top of gorge' is the wordplay.
'brim' becomes 'sure' (I can't explain this - if you can you should believe this answer much more).
'over' is an insertion indicator.
'top of' suggests taking the first letters.
The initial letter of 'gorge' is 'g'.
'sure' going around 'g' is 'SURGE'.
'to' is the link.
Can you help me to learn more?
(Other definitions for surge that I've seen before include "crest of a wave" , "Sudden influx" , "Sudden increase, gush" , "Sudden onward motion" , "Movement in crowd" .)