Managed a shower? Not I (3)
I believe the answer is:
ran
'managed' is the definition.
(both can mean organised or was in charge of)
'a shower? not i' is the wordplay.
'a shower?' becomes 'rain' (rainfall).
'not' suggests deleting specific letters.
'rain' with 'i' taken away is 'RAN'.
(Other definitions for ran that I've seen before include "Stood for election or managed" , "Flowed" , "Went fast" , "Organised" , "Administered" .)