Sure trick provided to lift depression (9)
I believe the answer is:
confident
'sure' is the definition.
('confident' can be similar in meaning to 'sure')
'trick provided to lift depression' is the wordplay.
'trick' becomes 'con' (I've seen this before).
'provided' becomes 'if'.
'to lift' says the letters should be written backwards (in a down clue, letters lift up).
'depression' becomes 'dent' ('dent' can be a synonym of 'depression'**).
'if' written backwards gives 'fi'.
'con'+'fi'+'dent'='CONFIDENT'
(Other definitions for confident that I've seen before include "Bold" , "Trusting firmly" , "Certain, sure" , "Feeling self-assured" , "5 [CERTAIN]" .)