Bear on mountain top is almost up to my neck (8-6)

'almost up to my neck' is the definition.
I don't know anything about this answer so I cannot tell whether this works.

'bear on mountain top' is the wordplay.
'bear' becomes 'shoulder' (both can mean to carry or take responsibility for).
'on' means one lot of letters go next to another (in a down clue, letters appear on others).
'mountain top' becomes 'height' (synonyms. I am not sure about the 'mountain' bit.).
'shoulder'+'height'='SHOULDER-HEIGHT'

'is' is the link.

Can you help me to learn more?