Shellfish, stemlike, regularly appearing back on land (7)

I believe the answer is:

winkles

'shellfish' is the definition.

'stemlike regularly appearing back on land' is the wordplay.
'regularly appearing' indicates alternate letters.
'back' says the letters should be written backwards.
'on' is a charade indicator (letters next to each other).
'land' becomes 'win'.
The alternating letters of 'stemlike' are 'selk'.
'selk' backwards is 'kles'.
'kles' put after 'win' is 'WINKLES'.

I've seen this clue in The Times.

Want a hint initially instead of a full solution? Install my app