Large tentacled creature raised behind pub is extraordinary (10)
I believe the answer is:
phenomenal
'extraordinary' is the definition.
(similar in meaning)
'large tentacled creature raised behind pub' is the wordplay.
'large' becomes 'L' (eg in clothes sizes).
'tentacled creature' becomes 'anemone' (I can't justify this - if you can you should give a lot more credence to this answer).
'raised' shows that the letters should be reversed in order (going up in a down clue).
'behind' means one lot of letters go next to another.
'pub' becomes 'ph' (abbreviation for Public House).
'l'+'anemone'='lanemone'
'lanemone' written backwards gives 'enomenal'.
'enomenal' after 'ph' is 'PHENOMENAL'.
'is' acts as a link.
Can you help me to learn more?
(Other definitions for phenomenal that I've seen before include "Remarkable" , "Unusual" , "Extraordinary - help one man (anag)" , "Incredible" , "Mind-blowing" .)