Timing mechanism spacemen utilised when trapped by alien (10)
I believe the answer is:
escapement
'timing mechanism' is the definition.
'escapement' can be an answer for 'mechanism' (escapement is a kind of mechanism). I'm not sure about the 'timing' bit.
'spacemen utilised when trapped by alien' is the wordplay.
I cannot really understand how this works, but
an anagram of 'spacemen' is 'scapemen' which is present in the answer.
'when' could be 'e' (I've seen this in other clues) and 'e' is found in the answer.
A single letter 't' remains which might be clued in a way I don't understand.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for escapement that I've seen before include "piano piece" , "Part of watch mechanism" , "Part of A Clockwork" , "Clock or watch mechanism" , "One-time flight" .)