Almost apologetic when sitting on the Spanish plant (6)
I believe the answer is:
sorrel
'spanish plant' is the definition.
'sorrel' can be an answer for 'plant' (sorrel is a kind of plant). I am not sure about the 'spanish' bit.
'almost apologetic when sitting on' is the wordplay.
'almost' means to remove the last letter (most of the word but not all of it).
'apologetic' becomes 'sorry' (I've seen this before).
'when sitting' becomes 'el' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'on' says to put letters next to each other.
'sorry' with its final letter removed is 'sorr'.
'sorr'+'el'='SORREL'
'the' is the link.
Can you help me to learn more?
(Other definitions for sorrel that I've seen before include "Type of horse" , "Acid-tasting salad leaf" , "Light brown: salad leaf" , "bay" , "Weed - colour of horse" .)