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 explain this - if you can you should give a lot more credence to this answer).
'raised' says the letters should be written in reverse (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' back-to-front is 'enomenal'.
'enomenal' after 'ph' is 'PHENOMENAL'.
'is' is the 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" .)