Old military group blocking entire interstellar transport option? (8)
I believe the answer is:
wormhole
'interstellar transport option?' is the definition.
Although both the answer and definition are singular nouns, I can't see how one could define the other.
'old military group blocking entire' is the wordplay.
'old' becomes 'o' (common abbreviation eg in OE for Old English).
'military group' becomes 'RM' (Royal Marines).
'blocking' means one lot of letters goes inside another (block can mean to plug a gap in something).
'entire' becomes 'whole' (similar in meaning).
'o'+'rm'='orm'
'orm' put into 'whole' is 'WORMHOLE'.
Can you help me to learn more?
(Other definitions for wormhole that I've seen before include "Cavity make in wood by burrowing larvae" , "Hypothetical link across space-time" , "could be ruined?" , "In theory, shortcut in space" , "Space made by burrowing limbless creature" .)