Furore when a drunken sot joins the marines (5)
I believe the answer is:
storm
'furore' is the definition.
(I've seen this before)
'a drunken sot joins the marines' is the wordplay.
'a drunken' indicates an anagram.
'joins' means one lot of letters go next to another.
'the marines' becomes 'RM' (abbreviation for 'Royal Marines').
'sot' anagrammed gives 'sto'.
'sto'+'rm'='STORM'
'when' is the link.
(Other definitions for storm that I've seen before include "violent assault" , "Very unfavourable climate" , "Feature of weather" , "Charge" , "Squall" .)