Pretty ordinary stretches of grassland (6,2,6)

I believe the answer is:

common or garden

I'm a little stuck... Click here to teach me more about this clue!

'pretty ordinary' is the definition.
'common or garden' can be an answer for 'ordinary' (I've seen this before). I am not sure about the 'pretty' bit.

I don't understand how the remainder of the clue works.

Can you help me to learn more?

(Other definitions for common or garden that I've seen before include "words associated with market" , "Unexceptional" , "usual type" , "Nothing special" , "choice of green space" .)

I've seen this clue in the Sydney Morning Herald.

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