What about getting in a couple of old stars? (3,4)

'of old stars?' is the definition.
The definition suggests a singular noun which matches the answer.

'what about getting in a couple' is the wordplay.
'what' becomes 'eh' (sound used to ask 'what?' or 'pardon?').
'about' shows that the letters should be reversed in order.
'getting in' means one lot of letters goes inside another.
'a couple' becomes 'twain' (archaic term for 'two').
'eh' in reverse letter order is 'he'.
'he' inserted inside 'twain' is 'THE WAIN'.

Can you help me to learn more?