Suspect increase lacks answer, being honest (7)
I believe the answer is:
sincere
'honest' is the definition.
('sincere' can be similar in meaning to 'honest')
'suspect increase lacks answer' is the wordplay.
'suspect' is an anagram indicator.
'lacks' is a deletion indicator.
'answer' becomes 'a' (abbreviation eg in Q and A).
'increase' with 'a' taken out is 'increse'.
'increse' is an anagram of 'SINCERE'.
'being' is the link.
(Other definitions for sincere that I've seen before include "Showing genuine feelings" , "Free from pretence" , "Unfeigned, genuine" , "Honest, frank" , "straightforward" .)