Mark speed of star? (9)
I believe the answer is:
celebrate
'mark' is the definition.
(thesaurus)
'speed of star?' is the wordplay.
I cannot really see how this works, but
'speed' could be 'rate' (the speed at which something happens) and 'rate' is located in the answer.
'star?' could be 'celeb' (I've seen this before) and 'celeb' is found within the answer.
This accounts for all the letters.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for celebrate that I've seen before include "Commemorate or eulogise" , "Throw a party" , "Have a party to mark a happy event" , "Have a party in honour of" , "Mark special event with festivities" .)