Well or poorly, it's ridiculously brave to go round Land's End (6)
I believe the answer is:
adverb
'well or poorly' is the definition.
('well' and 'poorly' are examples of adverbs)
'ridiculously brave to go round land's end' is the wordplay.
'ridiculously' indicates anagramming the letters (I've seen this in other clues).
'to go round' indicates putting letters inside.
'end' says to take the final letters.
The final letter of 'land' is 'd'.
'brave' anagrammed gives 'averb'.
'averb' placed around 'd' is 'ADVERB'.
'it's' acts as a link.
(Other definitions for adverb that I've seen before include "Word that modifies something other than a noun" , "Action word qualifier" , "Qualifying word in a sentence" , "Word such as 'madly'" , "Word that qualifies an action" .)