Avoids occasionally being seen in terribly poor condition (7)
I believe the answer is:
proviso
'condition' is the definition.
(I know that proviso is a type of condition)
'avoids occasionally being seen in terribly poor' is the wordplay.
'occasionally' indicates alternate letters.
'being seen in' means one lot of letters goes inside another.
'terribly' indicates an anagram.
The alternate letters of 'avoids' are 'vis'.
'poor' with letters rearranged gives 'proo'.
'vis' inserted within 'proo' is 'PROVISO'.
(Other definitions for proviso that I've seen before include "Condition, qualification" , "Stipulated condition" , "Rider" , "Condition for VIP or so" , "Stipulation (in contract)" .)