Doubly hard to catch swallow in wasteland (5)
I believe the answer is:
heath
'wasteland' is the definition.
(heath is a kind of wasteland)
'doubly hard to catch swallow' is the wordplay.
'doubly' shows that letters should be duplicated.
'hard' becomes 'h'.
'to catch' means one lot of letters goes inside another.
'swallow' becomes 'eat' (I've seen this before).
'h' duplicated is 'hh'.
'hh' enclosing 'eat' is 'HEATH'.
'in' is the link.
(Other definitions for heath that I've seen before include "Statesman" , "Barren open land" , "Ex-Tory PM" , "Shrubby area of open country" , "On which a weird trio met" .)