Essentially female row about small dog (7)
I believe the answer is:
mastiff
'dog' is the definition.
(mastiff is a kind of dog)
'essentially female row about small' is the wordplay.
'essentially' indicates the central letters.
'row' becomes 'tiff' (tiff is a kind of row).
'about' says to put letters next to each other.
'small' becomes 's' (abbreviation - e.g. clothes size).
The middle of 'female' is 'ma'.
'tiff' put after 's' is 'stiff'.
'ma'+'stiff'='MASTIFF'
(Other definitions for mastiff that I've seen before include "Powerful breed of watchdog" , "Powerful dog breed" , "Strong breed of dog" , "one of his best friends?" , "Large, powerful, short-haired dog" .)