Hold back and relax with shower (8)
I believe the answer is:
restrain
'hold back' is the definition.
(synonyms)
'relax with shower' is the wordplay.
'relax' becomes 'rest' (to relax is to have a rest).
'with' is a charade indicator (letters next to each other).
'shower' becomes 'rain' (synonyms).
'rest'+'rain'='RESTRAIN'
'and' is the link.
(Other definitions for restrain that I've seen before include "In arrest (anagram)" , "Limit" , "Prevent (from excess)" , "bottle up" , "Manacle" .)