Shouting may finish the Spanish fish (7)
I believe the answer is:
'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'.
(Other definitions for yelling that I've seen before include "Uttering loud cries", "Screaming", "Hollering, howling", "Shouting loudly", "Bellowing".)