Stop and relax with a shower (8)
I believe the answer is:
restrain
'stop' is the definition.
(I've seen this before)
'relax with a shower' is the wordplay.
'relax' becomes 'rest' (to relax is to have a rest).
'with' means one lot of letters go next to another.
'a shower' becomes 'rain' (synonyms).
'rest'+'rain'='RESTRAIN'
'and' acts as a link.
(Other definitions for restrain that I've seen before include "Manacle" , "Tie up - arrest" , "Keep under control" , "Stop" , "Arrest - confine - subdue" .)