Fantastic teacher shone no end, a dependable sort? (5,6)
I believe the answer is:
sheet anchor
'a dependable sort?' is the definition.
(I've seen this before)
'fantastic teacher shone no end' is the wordplay.
'fantastic' indicates anagramming the letters (a fantastic or improbable ordering of the letters).
'no end' means to remove the last letter.
'teacher'+'shone'='teachershone'
'teachershone' with its last letter taken off is 'teachershon'.
'teachershon' anagrammed gives 'SHEET-ANCHOR'.
(Other definitions for sheet anchor that I've seen before include "Ship's emergency item; last refuge" , "Something ship relies upon in emergencies" , "Emergency naval item" , "dependable sort" , "It may prevent ship hitting side of harbour" .)