Provide with a source of endless wonder (5)
I believe the answer is:
endow
'provide with' is the definition.
(I've seen this before)
'a source of endless wonder' is the wordplay.
'a source of' is an anagram indicator.
'endless' means to remove the last letter.
'wonder' with its final letter removed is 'wonde'.
'wonde' anagrammed gives 'ENDOW'.
(Other definitions for endow that I've seen before include "Provide capital to ensure an income for an institution" , "Provide with a source of income" , "provide permanent finance for ..." , "Give funding to establish (something)" , "Provide with an income, say a college" .)