Pick up a letter with an enclosure (5)
I believe the answer is:
scoop
'pick up' is the definition.
(thesaurus)
'a letter with an enclosure' is the wordplay.
'a letter' becomes 's' (**).
'with' says to put letters next to each other.
'an enclosure' becomes 'coop' (coop is a kind of enclosure).
's'+'coop'='SCOOP'
(Other definitions for scoop that I've seen before include "Piece of news that no-one else has" , "Large ladle" , "Press exclusive" , "bail" , "Exclusive - ice cream server" .)