Revolutionary in charge with tough-looking tank (7)
I believe the answer is:
cistern
'tank' is the definition.
(cistern is a kind of tank)
'revolutionary in charge with tough-looking' is the wordplay.
'revolutionary' says the letters should be written backwards.
'in charge' becomes 'ic'.
'with' means one lot of letters go next to another.
'tough-looking' becomes 'stern'.
'ic' reversed gives 'ci'.
'ci'+'stern'='CISTERN'
(Other definitions for cistern that I've seen before include "Toilet water reservoir" , "Toilet tank [ital]" , "Tank, reservoir" , "Tank - sac of body fluid" , "WC water tank" .)