Stick together stuff in cutting semi-precious stone (11)

'stick together' is the definition.
(thesaurus)

'stuff in cutting semi-precious stone' is the wordplay.
'stuff' becomes 'glut' ('glut' can be a synonym of 'stuff'**).
'cutting' is an insertion indicator (some letters cut their way into a word).
'semi-precious stone' becomes 'agate' (I've seen this before).
'glut'+'in'='glutin'
'glutin' put into 'agate' is 'AGGLUTINATE'.