Access a couple of pages on freshwater fish (8)
I believe the answer is:
Here is my best explanation:
'access' is the definition.
('approach' can be a synonym of 'access')
'a couple of pages on freshwater fish' is the subsidiary indication.
'couple of' shows that letters should be duplicated.
'pages' becomes 'p'.
'on' is a charade indicator (letters next to each other).
'freshwater fish' becomes 'roach' (I've seen this before**).
'p' duplicated is 'pp'.
(Other definitions for approach that I've seen before include "Come towards", "Near", "Come near - means of access", "Avenue", "Get closer to", "Come closer", "Move towards", "Advance towards", "Drae near" and "Come near or nearer to".)