'Thank Heaven!' (clutches cross) (4)
I believe the answer is:
ankh
'cross' is the definition.
(thesaurus)
'thank heaven clutches' is the wordplay.
'clutches' indicates a hidden word (I've seen 'clutching' mean this).
'ANKH' is hidden in the letters of 'thank heaven'.
(Other definitions for ankh that I've seen before include "Cross with a loop at the top, symbol of life in ancient Egypt" , "Egyptian cross" , "Ancient Egyptian symbol of life - khan (anag)" , "Waylay" , "Hank (anag) - cross symbolising eternal life" .)