Unusual angle given by eccentric (3,4)
I believe the answer is:
odd fish
'eccentric' is the definition.
(I've seen this before)
'unusual angle given' is the wordplay.
'unusual' becomes 'odd' (similar in meaning).
'angle' becomes 'fish' (synonyms).
'given' says to put letters next to each other.
'odd'+'fish'='ODD FISH'
'by' acts as a link.
(Other definitions for odd fish that I've seen before include "Eccentric person of piscine sort" , "Peculiar person" , "Person of strange habits" .)