Converted in temple welcoming first of missions to carry out (9)
I believe the answer is:
implement
'carry out' is the definition.
(I've seen this before)
'converted in temple welcoming first of missions' is the wordplay.
'converted' indicates anagramming the letters.
'welcoming' is an insertion indicator (in sense of 'inviting in').
'first of' says to take the initial letters.
The first letter of 'missions' is 'm'.
'in'+'temple'='intemple'
'intemple' with letters rearranged gives 'impleent'.
'impleent' enclosing 'm' is 'IMPLEMENT'.
'to' is the link.
(Other definitions for implement that I've seen before include "Device" , "Execute" , "Put into effect; tool" , "Enforce, carry out" , "Put into action - utensil" .)