General’s promise to fence in lake with fish (9)

'general's' is the definition.
(synonyms)

'promise to fence in lake with fish' is the wordplay.
'promise' becomes 'word' (as in 'I give you my word').
'to fence in' indicates putting letters inside (inserted letters are fenced in).
'lake' becomes 'L' (geographical abbreviation).
'with' means one lot of letters go next to another.
'fish' becomes 'wide' (I can't justify this - if you can you should give a lot more credence to this answer).
'word' going around 'l' is 'world'.
'world'+'wide'='WORLDWIDE'