Plants kiss on middle of cheek: love comes first, absolutely (2-4)

'plants' is the definition.
(ox-eye is a kind of plant)

'kiss on middle of cheek love comes first absolutely' is the wordplay.
'kiss on' becomes 'x' (X can represent a kiss. I am not sure about the 'on' bit.).
'middle of' indicates the central letters.
'love' becomes 'o' (love means zero in tennis).
'comes first' is a charade indicator (letters next to each other).
'absolutely' becomes 'yes' (both can be used to give an affirmative answer).
The central letter of 'cheek' is 'e'.
'x'+'e'='xe'
'xe' after 'o' is 'oxe'.
'oxe'+'yes'='OX-EYES'