It's hard to carry, making you grumpy (5)
I believe the answer is:
cross
'grumpy' is the definition.
(synonyms)
I can't explain the remainder of the clue.
Can you help me to learn more?
(Other definitions for cross that I've seen before include "Annoyed; symbol" , "Traverse - displeased" , "means of execution" , "Grouchy" , "frustrated?" .)