It's tough, being deceived outright (4)
I believe the answer is:
hard
'it's tough' is the definition.
(synonyms)
I can't explain the rest of the clue.
Can you help me to learn more?
(Other definitions for hard that I've seen before include "Solid; difficult" , "Difficult - firm" , "Firm; demanding; stern" , "Tough - difficult" , "Novel featuring Mr Gradgrind" .)