Intermittently clear day with nothing on, sweetheart (4-4)

'sweetheart' is the definition.
(I've seen this before)

'intermittently clear day with nothing' is the wordplay.
'intermittently' indicates alternate letters.
'with' means one lot of letters go next to another.
'nothing' becomes 'love' (love means zero in tennis).
'clear'+'day'='clearday'
The alternating letters of 'clearday' are 'lady'.
'lady'+'love'='LADY-LOVE'

'on' is the link.