Rocket scientists heading for landing on a central feature (5)
I believe the answer is:
stone
'rocket' is the definition.
(thesaurus)
'scientists heading for landing on a central feature' is the wordplay.
'heading' indicates taking the first letters (head could mean the top letter).
'for' says to put letters next to each other.
'landing on' means one lot of letters go next to another (in a down clue, some letters go on top of others).
'a' becomes 'one'.
'central' indicates the central letters.
The middle of 'feature' is 't'.
The initial letter of 'scientists' is 's'.
'one' after 't' is 'tone'.
's'+'tone' is 'STONE'.
(Other definitions for stone that I've seen before include "diamond, say" , "Little rock" , "Imperial unit of weight" , "See 1" , "See 21" .)