Shouting may finish the Spanish fish (7)
I believe the answer is:
yelling
'shouting' is the definition.
(yelling is a kind of shouting)
'may finish the spanish fish' is the wordplay.
'finish' says to take the final letters.
'the spanish' becomes 'el' ('the' in Spanish).
'fish' becomes 'ling' (ling is a kind of fish).
The final letter of 'may' is 'y'.
'y'+'el'+'ling'='YELLING'
(Other definitions for yelling that I've seen before include "Uttering loud cries" , "Bellowing" , "Shouting loudly" , "Hollering, howling" , "Screaming" .)