Short pause about to be welcomed by swimmer (8)
I believe the answer is:
breather
'short pause' is the definition.
(I've seen this before)
'about to be welcomed by swimmer' is the wordplay.
'about' becomes 're' (regarding).
'to be welcomed by' is an insertion indicator (I've seen this in other clues).
'swimmer' becomes 'bather' ('bather' can be a synonym of 'swimmer'**).
're' put into 'bather' is 'BREATHER'.
(Other definitions for breather that I've seen before include "One who inspires" , "Short pause for rest" , "Informally a pause for rest - or to take in air" , "Brief pause for rest" , "Recovery time" .)