Bug in water very close to surface (5)
I believe the answer is:
peeve
'bug' is the definition.
(I've seen this before)
'water very close to surface' is the wordplay.
'water' becomes 'pee' (synonyms).
'very' becomes 'v' (abbreviation).
'close to' says to take the final letters (the 'close' to the word).
The final letter of 'surface' is 'e'.
'pee'+'v'+'e'='PEEVE'
'in' is the link.
(Other definitions for peeve that I've seen before include "Get annoyed" , "grouse" , "Vex" , "cause irritation" , "Cause resentment" .)