Takes off? He would shortly be on board? (5)
I believe the answer is:
sheds
'takes off?' is the definition.
(I've seen this in another clue)
'he would shortly be on board?' is the wordplay.
'he' becomes 'shes' (I can't explain this - if you can you should believe this answer much more).
'shortly' says to take the final letters.
'be on board?' is an insertion indicator (inserted letters are taken on board).
The last letter of 'would' is 'd'.
'shes' enclosing 'd' is 'SHEDS'.
Can you help me to learn more?
(Other definitions for sheds that I've seen before include "Single-storey outbuildings" , "Casts off the outhouses?" , "Gets rid" , "Small huts as used in gardens" , "Discards" .)