Love, jumpy but not very demanding (7)
I believe the answer is:
onerous
'demanding' is the definition.
(onerous means difficult or demanding)
'love jumpy but not very' is the wordplay.
'love' becomes 'o' (love means zero in tennis).
'jumpy' becomes 'nervous' (synonyms).
'but not' is a deletion indicator.
'very' becomes 'v' (common abbreviation).
'nervous' with 'v' taken out is 'nerous'.
'o'+'nerous'='ONEROUS'
(Other definitions for onerous that I've seen before include "Involving much work" , "Involving a great deal of effort" , "Burdensome as duty may be" , "Toilsome" , "Heavy and hard to bear" .)