Fall badly beneath shower head and squeal (5,3,5)
I believe the answer is:
spill the beans
'squeal' is the definition.
(thesaurus)
'fall badly beneath shower head' is the wordplay.
'fall' becomes 'spill' (synonyms).
'badly' indicates an anagram.
'head' indicates taking the first letters.
The first letter of 'shower' is 's'.
'beneath' is an anagram of 'thebean'.
'spill'+'thebean'+'s'='SPILL THE BEANS'
'and' acts as a link.
(Other definitions for spill the beans that I've seen before include "Reveal secret information" , "Blab" , "Divulge secret" , "Give away secrets" , "To sing" .)