Found it tough, showing the same thing (5)
I believe the answer is:
ditto
'the same thing' is the definition.
(I've seen this before)
'found it tough showing' is the wordplay.
'showing' indicates a hidden word.
'DITTO' can be found hidden inside 'found it tough'.
(Other definitions for ditto that I've seen before include "As per previous" , "Repeat (instruction)" , "The same thing" , "As given above" , "Two dots indicating the same again" .)