I sat first, dined on date, and filled up (8)
I believe the answer is:
satiated
'filled up' is the definition.
'satiated' can be an answer for 'filled' ('satiate' can be a synonym of 'fill'). I am not sure about the 'up' bit.
'i sat first dined on date' is the wordplay.
'first' says to put letters next to each other.
'dined on' becomes 'ate' (I've seen this in another clue).
'date' becomes 'd' (common abbreviation eg in DOB, date of birth).
'i' put after 'sat' is 'sati'.
'sati'+'ate'+'d'='SATIATED'
'and' is the link.
Can you help me to learn more?
(Other definitions for satiated that I've seen before include "Too full, having eaten excessively" , "Fully satisfied" , "Fully replete" , "Glutted, full of food" , "Glutted or cloyed with excess (8)" .)