Animal in a large herd, mostly close to sea (6)
I believe the answer is:
alpaca
'animal' is the definition.
(South American animal)
'a large herd mostly close to sea' is the wordplay.
'large' becomes 'L' (eg in clothes sizes).
'herd mostly' becomes 'pac' (I can't explain this - if you can you should give a lot more credence to this answer).
'close to' suggests the final letters (the close/ending of).
The last letter of 'sea' is 'a'.
'a'+'l'+'pac'+'a'='ALPACA'
'in' acts as a link.
Can you help me to learn more?
(Other definitions for alpaca that I've seen before include "Type of llama" , "S American animal related to llana" , "S American mammal related to the llama" , "Llama relation" , "Llama relative, valued for it's wool" .)