Get a welcome run and declare (4)
I believe the answer is:
aver
'declare' is the definition.
(averring is a kind of declaring)
'get a welcome run' is the wordplay.
'get' means one lot of letters go next to another.
'a welcome' becomes 'ave' (I've seen this before).
'run' becomes 'r' (cricket abbreviation).
'ave'+'r' is 'AVER'.
'and' acts as a link.
(Other definitions for aver that I've seen before include "claim" , "'Affirm, assert (4)'" , "Declare or insist" , "Firmly maintain" , "Say firmly, declare" .)