Bottled up in feelings for swimmer (3)
I believe the answer is:
eel
'swimmer' is the definition.
(eel is a kind of aquatic vertebrate)
'bottled up in feelings' is the wordplay.
'EEL' is hidden in amongst the letters.
But, I'm not sure how the hidden word is indicated.
'for' is the link.
Can you help me to learn more?
(Other definitions for eel that I've seen before include "Snake-like sea creature" , "Creature like conger or moray" , "Moray or electric, for instance" , "Apode" , "Slippery type" .)