A medium seeing adventurous girl almost restraining sob (7)
I believe the answer is:
acrylic
'a medium' is the definition.
(artistic medium)
'adventurous girl almost restraining sob' is the wordplay.
'adventurous girl' becomes 'Alice' (main character in Alice's Adventures in Wonderland).
'almost' means to remove the last letter (most of the word but not all of it).
'restraining' is an insertion indicator.
'sob' becomes 'cry' (I've seen this in another clue).
'alice' with its last letter taken off is 'alic'.
'alic' going around 'cry' is 'ACRYLIC'.
'seeing' is the link.
(Other definitions for acrylic that I've seen before include "Pungent acid" , "fibre that's synthetic" , "Synthetic fabric" , "Type of paint or textile fibre" , "Synthetic resin or fibre used for textiles" .)