Fellows put in perfect crane on board, it's sworn in court (9)
I believe the answer is:
affidavit
'board it's sworn in court' is the definition.
I can't tell whether this defines the answer.
'fellows put in perfect crane' is the wordplay.
'fellows' becomes 'ff'.
'put in' means one lot of letters goes inside another.
'perfect' becomes 'ai' (I've seen this in other clues).
'crane' becomes 'davit' (davit is a kind of crane).
'ff' going within 'ai' is 'affi'.
'affi'+'davit'='AFFIDAVIT'
'on' is the link.
Can you help me to learn more?
(Other definitions for affidavit that I've seen before include "Instrument's" , "legal document" , "Sworn court statement" , "Written declaration made under oath" , "Declaration before notary" .)