Grant UFOs have crashed round Cuba's capital (9)
I believe the answer is:
vouchsafe
'grant' is the definition.
(vouchsafing is a kind of granting)
'ufos have crashed round cuba's capital' is the wordplay.
'crashed' is an anagram indicator.
'round' means one lot of letters goes inside another.
'capital' suggests taking the first letters.
The initial letter of 'cuba' is 'c'.
'ufos'+'have'='ufoshave'
'ufoshave' anagrammed gives 'vouhsafe'.
'vouhsafe' going around 'c' is 'VOUCHSAFE'.
(Other definitions for vouchsafe that I've seen before include "Give in gracious manner - have focus on" , "Condescend to grant" , "Deign to give" , "Give or grant, perhaps in condescending manner" , "Grant graciously" .)