Like old houses, almost plentiful in Reading (7)

'like old houses' is the definition.

'almost plentiful in reading' is the wordplay.
'almost' means to remove the last letter (most of the word but not all of it).
'plentiful' becomes 'ample' ('ample' can be a synonym of 'plentiful').
'in' means one lot of letters goes inside another.
'reading' becomes 'lit' (abbreviation for literature).
'ample' with its final letter taken off is 'ampl'.
'ampl' inserted within 'lit' is 'LAMPLIT'.