Conservative first only encountered an astronomical object (5)

I believe the answer is:

comet

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'an astronomical object' is the definition.
'comet' can be an answer for 'object' (comet is a kind of object). I'm not sure about the 'an astronomical' bit.

'conservative first only encountered' is the wordplay.
'conservative' becomes 'C' (UK political abbreviation).
'first only' becomes 'o' (1st letter of 'only').
'encountered' becomes 'met' ('meet' can be a synonym of 'encounter').
'c'+'o'+'met'='COMET'

Can you help me to learn more?

(Other definitions for comet that I've seen before include "body found in space" , "Shooting star" , "Celestial body - early jet aircraft" , "Tailed space traveller" , "Traveller round sun" .)

I've seen this clue in The Daily Express.

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