Mother takes girl back to a Spanish resort (6)
I believe the answer is:
Here is my best explanation:
'a spanish resort' is the definition.
'mother takes girl back to' is the subsidiary indication.
'mother' becomes 'ma' (ma is a kind of mother).
'takes' says to put letters next to each other.
'girl' becomes 'gal' ('gal' can be a synonym of 'girl'**).
'back' is a reversal indicator.
'to' becomes 'a' (I've seen this in other clues).
'gal' reversed gives 'lag'.
(Other definitions for malaga that I've seen before include "Sweet wine; Spanish port", "Andalusian city", "Spanish port and resort town", "Costa del Sol resort", "Southern Spanish city and resort", "City of Andalusia", "Andalusian port; wine", "Army rank; not shared", "Spanish city and holiday resort" and "Resort in Andalusia".)