Anyhow, worms have a right to get into vegetables! (7)

'vegetables' is the definition.
(marrow is a kind of vegetable)

'anyhow worms have a right to get' is the wordplay.
'anyhow' indicates an anagram.
'have' says to put letters next to each other.
'right' becomes 'r' (common abbreviation).
'to get' indicates putting letters inside.
'worms'+'a'='wormsa'
'wormsa' is an anagram of 'marows'.
'marows' placed around 'r' is 'MARROWS'.

'into' acts as a link.