Vestment certain to have a broken clip inside (8)
I believe the answer is:
surplice
'vestment' is the definition.
(I know that surplice is a type of vestment)
'have a broken clip inside' is the wordplay.
'have' becomes 'sure' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'a broken' indicates an anagram.
'inside' is an insertion indicator.
'clip' anagrammed gives 'plic'.
'sure' placed around 'plic' is 'SURPLICE'.
'certain to' acts as a link.
I am not very happy about this link. Some or all of it may belong to another bit of the clue.
Can you help me to learn more?
(Other definitions for surplice that I've seen before include "Loose white ecclesiastical garment" , "Loose white clerical vestment" , "I scruple to wear priestly garment" , "Christian vestment" , "Clerical or choral garment" .)