End up with horrible mess under something sticky -- oh dear! (8,2)
I believe the answer is:
goodness me
'oh dear' is the definition.
I know nothing about this answer so I cannot judge whether this works.
'end up with horrible mess under something sticky' is the wordplay.
'up' says the letters should be written backwards (in down clue: letters go upwards).
'with' is an insertion indicator.
'horrible' is an anagram indicator.
'under' says to put letters next to each other.
'something sticky' becomes 'goo' (**).
'end' reversed gives 'dne'.
'mess' is an anagram of 'essm'.
'dne' enclosing 'essm' is 'dnessme'.
'dnessme' after 'goo' is 'GOODNESS ME'.
Can you help me to learn more?
(Another definition for goodness me that I've seen is " Well, well!".)