Dean occasionally sits on stripy plastic during such outings (3,5)
I believe the answer is:
day trips
'such outings' is the definition.
(day trips are outings)
'dean occasionally sits on stripy plastic' is the wordplay.
'occasionally' indicates alternate letters (letters taken at regular intervals or occasions).
'sits on' means one lot of letters go next to another.
'plastic' indicates anagramming the letters (plastic can mean easily moulded).
The alternating letters of 'dean' are 'da'.
'stripy' is an anagram of 'ytrips'.
'da'+'ytrips'='DAY TRIPS'
'during' acts as a link.
I am not very happy about this link. It may belong to another bit of the clue.
Can you help me to learn more?
(Other definitions for day trips that I've seen before include "spins" , "visits" .)