Nomad swims regularly in watering hole (5)
I believe the answer is:
oasis
'watering hole' is the definition.
(I've seen this before)
'nomad swims regularly' is the wordplay.
'regularly' indicates alternate letters (regularly take one letter, leave next etc.).
'nomad'+'swims'='nomadswims'
The alternating letters of 'nomadswims' are 'OASIS'.
'in' is the link.
(Other definitions for oasis that I've seen before include "Green area in desert" , "Place of rest in the midst of gloom" , "Famous group" , "Florist's foam" , "Pop group" .)