Implement, for all to see, capable of being stretched, endlessly (7)
I believe the answer is:
utensil
'implement' is the definition.
(utensil is a kind of implement)
'for all to see capable of being stretched endlessly' is the wordplay.
'for all to see' becomes 'u' (universal dvd certificate).
'capable of being stretched' becomes 'tensile' (I've seen this before).
'endlessly' means to remove the last letter.
'tensile' with its final letter taken away is 'tensil'.
'u'+'tensil'='UTENSIL'
(Other definitions for utensil that I've seen before include "Can opener, for example" , "E.g. colander" , "vessel" , "A container for kitchen use" , "A kitchen pot or pan" .)