No hiding space over introduction to star signs (5)
I believe the answer is:
omens
'signs' is the definition.
(I know this)
'no hiding space over introduction to star' is the wordplay.
'hiding' means one lot of letters goes inside another.
'space' becomes 'em' (in typography, a space as wide as a letter 'm').
'over' says the letters should be written in reverse.
'introduction to' says to take the initial letters.
The first letter of 'star' is 's'.
'no' placed around 'em' is 'nemo'.
'nemo' backwards is 'omen'.
'omen'+'s'='OMENS'
(Other definitions for omens that I've seen before include "Signs or warnings for the future" , "Portents, prophetic signs" , "Augurs" , "Harbingers, portents" , "Signs of things to come" .)