Love? Turned on by slender girls primarily (7)
I believe the answer is:
nothing
'love?' is the definition.
(I've seen this before)
'turned on by slender girls primarily' is the wordplay.
'turned' says the letters should be written in reverse.
'by' is a charade indicator (letters next to each other).
'slender' becomes 'thin' ('thin' can be similar in meaning to 'slender'**).
'primarily' indicates taking the first letters.
The initial letter of 'girls' is 'g'.
'on' in reverse letter order is 'no'.
'no'+'thin'+'g'='NOTHING'
(Other definitions for nothing that I've seen before include "Something of no concern" , "Zero, nil" , "Unimportant item" , "Naught, nil, nix" , "unimportant or > unintelligible" .)