Holly sees priest returning to cross (4)
I believe the answer is:
ilex
'holly' is the definition.
(I've seen this before)
'priest returning to cross' is the wordplay.
'priest' becomes 'eli' (I've seen this before).
'returning' says the letters should be written in reverse.
'to cross' becomes 'x'.
'eli' back-to-front is 'ile'.
'ile'+'x'='ILEX'
'sees' is the link.
(Other definitions for ilex that I've seen before include "'Tree group, includes holly (4)'" , "Tree of the genus that includes holly" , "The holly family of trees" , "The holm-oak" , "Genus of trees that includes hollies" .)