Took a seat to hug partner, discontented with fish (5)
I believe the answer is:
sprat
'fish' is the definition.
(sprat is a kind of fish)
'took a seat to hug partner discontented' is the wordplay.
'took a seat' becomes 'sat' (I've seen this before).
'to hug' means one lot of letters goes inside another (inserted letters are hugged).
'discontented' means to remove the middle letters (the word's contents are removed).
'partner' with its middle taken out is 'pr'.
'sat' going around 'pr' is 'SPRAT'.
'with' acts as a link.
(Other definitions for sprat that I've seen before include "Mackerel bait?" , "Small fish, sardine, say" , "Small fish (used to catch mackerel?)" , "It's set to catch a mackerel" , "Herring's smaller relative" .)