It's tough, being caught outright! (4)
I believe the answer is:
hard
'it's tough' is the definition.
(synonyms)
I don't understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for hard that I've seen before include "Firm, rigid, road leading to foreshore" , "Firm; demanding; stern" , "Unyielding" , "Intensely" , "Strenuous" .)